The writing was on the wall for a long time, but I didn't want to believe it. I have been using Sente as my reference manager for over 5 years and loved it. But over two years ago, the developers stopped blogging. Then over a year ago, the forum closed down. Then the support emails stopped. It kept working, including its syncing feature, and I hoped that perhaps the developer was just on an extended vacation. Recently, I held my breath as I updated to High Sierra and updated to Mellel 4. Still it worked. But then the syncing stopped. In a last-ditch attempt, I tried again to contact the developer – I even found a phone number online. No luck. I could delude myself no longer. I had to migrate.

Luckily, I knew that I had a wonderful option. Bookends has been a high-rated reference manager for many years, I am even a former user. And the developer of Bookends, anticipating the demise of Sente, has improved its ability to import references from Sente. But despite this all, I still had to put in a lot of grunt work to get all of my information, and especially my PDF highlights, into Bookends.

For those, like me, who are now making the move to Bookends from Sente, here are the steps I had to go through. Before I get to that, a few other comments.

Things that I will miss from Sente

Being able to double-click and go into a full window reading view was excellent, as was the ability to open a tab to browse. *edit* The recent release of Bookends 13 added a full screen reading ability, which I'm very happy about.
Attachment and Annotation. By far this is my biggest lament, but I am already adjusting to Bookends and the way it does things.
While I will get used to and enjoy the notecard stream, in particular being able to add tags and be able to cite directly from them, Sente had a custom highlighter and notes that remains unparalleled. Being able to quickly choose to quote and choose the color was in a pop-up immediately when highlighting was excellent.
The Bookends notestream is quite different and will take some getting used to. I imagine that former Sente users will most use the “Highlight Selection and Make Bookends Notecard” from the annotations menu. What remains somewhat clunky in this process, in my opinion, is that this creates 2 notecards, one to links to the PDF (so you can jump to the spot) and the other the actual notecard to take your notes. I so wish these were combined into a single item so that the note stream wouldn’t be cluttered. This can be hidden in the annotations menu at the bottom, but clicking on the notecard doesn’t jump to the spot in the PDF. Thankfully, you can still jump to the notecard spot in the PDF via a shortcut key, or by right-clicking the notecard and choosing "Find in PDF."
Whereas Sente had the automatic layout for title, page, quote, and notes, only the page and quote are automatic in Bookends. For the rest you need to learn the syntax Bookends utilizes. And unless I’m doing something wrong, Bookends doesn’t know automatically which page is being cited, it takes the page of the PDF, rather than the actual page number (pulled from the page range). This creates extra work. *edit* The recent release of Bookends 13 has changed this functionality to reference the actual page number, which is fantastic.
Sente’s auto-links were beyond wonderful and helpful. Auto-links built off of the DOI or ISBN, this was a great way to see other web metadata and especially being able to do a book search in google books.

Bookends Features that I Look Forward To

I actually started out as a Bookends user so I am very familiar and like the app. I have never had any hesitation in recommending Bookends to people. The above issues are the reasons I ultimately moved to Sente. But since my departure from Bookends, some additions have been made that I look forward to utilizing or making use of again.

Bookends importing has always been better than Sente overall. The Bookends Browser works extremely well and I am very happy with it.
Bookends has always worked amazingly well with Mellel, my Word Processor of choice. The integration has only gotten better over the years.
Bookends does cloud sync with iCloud now, and has added a very nice iOS app. Of course this means that I have to rely on iCloud syncing which isn't always 100%, but that is getting better too.

My Steps For Migrating Data from Sente to Bookends

Step 1: Duplicate your Sente library for safe keeping

Duplicate your Sente library, as the steps below will slowly delete items from the Sente library.

Step 2: Prepare Bookends Library to match your Sente library

Replicate your “Sente Statuses” from the Library setup in Bookends preferences>Lists
Replicate your bookmarks from “Web Bookmarks” from the Library setup in the Bookends bookmarks found when you click on an item and open the Browser
Replicate your Sente reference types in Bookends preferences Refs>Reference types (I recommend not changing any - leave those that are there, and any new ones you need)
Replicate your Sente Reference Type fields for any special fields you may use
Decide how you want your PDFs named. Unlike Sente, which does a really nice folder hierarchy, Bookends places them all in a single folder. I created a simple format file for Bookends to use the last name date - short title for all attached PDFs.
You can customize the summary view in the Preferences to look how you would like it. (I’m happy with the default, but may create my own format for the summary view in the future)

Step 3: Confirm your Attachments

Unfortunately for some of us, Sente may have done us wrong at some point – or the use of multiple computers might mean that some of your attachments aren’t on the computer you are using for the migration. Hopefully none of them are MIA (i.e. sitting on Sente’s now-defunct server). If you have some missing, make a list of them in some way (static group or a bibliography) in order to check another computer.

Step 4 (optional) : Attachments

People will need to decide if they are happy to keep the notes/quotes made without them being linked to the PDF. When importing directly from Sente to Bookends, Bookends will bring all of the notes over into its notestream, but the highlights and connection to the PDF in Sente will be stripped, as this was stored in a special way in Sente.

After thinking about this, I made the decision to put in the grunt-work of keeping my highlights for the bulk of my PDFs. The result was the following process:

Scan through your Sente library. Whenever you find an entry with the attachment and notes icon, I added a quick tag.
I then imported this group into Sente, and then went through each one, adding new highlights in Bookends. After doing this, I deleted each item from Sente.

Step 5 (optional): Set up Sync

If you want your library and attachments cloud synced and available on your iOS devices, you need to purchase the app, then purchase the yearly subscription.
In Bookends you will see a cloud icon to sign in to iCloud and enable the sync. If you have lots of PDFs you will need to pay for additional iCloud storage as well. Alternatively, you can use another sync service (dropbox, google drive, etc.) for your attachments and custom folders.
Alternatively if you do not have iCloud, you can also sync Bookends over wifi.

Procedure for Moving Library Over

Keep in mind that the things which do not get transferred over are Sente statuses (Bookends labels) and the reference type does not always come over correctly, particularly for special citation types that you may use. You are safe, as far as I can tell, with the standard Books, Book chapters, edited book, journals.

Bookends has made it very easy for Sente users to import. In Bookends, go to File>Import>from Sente and click okay. Then highlight the items you want to import in Sente and click OK on the little dialogue button you will see.

I highly recommend that you take 1 of each type of reference in your library and import it to Bookends. Inspect and make sure that all of the info came over and into the expected fields. For the most part this should be fine, but if you have customized Sente, this may complicate the process. In my case, dissertations didn’t bring the info over correctly. Luckily, Bookends is amazing and mass changes, and I was able to correct the problems quickly.
First move over from the group you’ve made for Attachments (see below). Move them over by status>type to ensure that they get moved over as the right type of citation. Upon bringing them in, THEY WILL BE HIGHLIGHTED. IMMEDIATELY use the correct shortcut to apply the label necessary. there is no other easy way to mass change labels later.
**As an alternative, you can use temporary tags in Sente to mark your labels and different Reference Types. This would allow you to import your entire Sente library at once and then fix your labels and reference types doing a search for those temporary tags in Bookends. The reason I chose to do it this way (i.e. without the temporary tags) is to minimize the chance of import errors which can occur from time to time.
Go back to Sente and delete each of these imported citations to remove them from the database.
Once you are done with these in the group, go to the folder with the exported PDFs on your desktop, and attach each of them to the correct citation.
Now continue the process through your status groups, bringing them in by type to ensure they come through correctly by type and immediately assigning the label. The easiest way to do this is to use the Status filters on the right and then using Sente’s list view and click on the Type column to organize them by type.
One other thing I noted during the process is that at times some “stray code” came in as attachments. This may not bother people, but it annoyed me. So I had the added process of going through Bookends and whenever there was a double paperclip icon, I went in the BE Inspector to delete the stray code attachment.
Bookends is great at doing mass find and replaces. One thing I needed to do was replace <sup> with ^, and </sup> with ^ . This is how superscripts are indicated in Bookends. Any ampersands come through as “&” so replace those as well. In my abstracts and notes I frequently used line breaks, which come through as <br>, so I replaced them.

Those are the steps I took. I've unfortunately had to spend an inordinate amount of time on the process, but it is done and I'm now the proud user of Bookends.