I'm new to this forum and, in fact, also new to Bookends. That didn't stop me from migration all my +1500 references plus attachments to Bookends in just a few days (did a bit of clean-up too, preparing my sabbatical). After using Sente for a few years, I started to dislike the UI and lack of support; then moved to Zotero, which works fine but also gave me some problems of customisation. Finally decided to try both Papers and Bookends—the first was too buggy for my taste and Bookends was just perfect. I'm actually kicking myself for not trying it earlier. It's a terrific app and its sidekick (BoT) works great for reading and annotating files on the go... (looking forward for further customisation of the sync, though: sync all refs, but only download specific groups)
Anyway—two of my usual search and import refs workflows are:
– Open Alfred and search Google Scholar from it (normally title of needed ref). The webpage opens in Safari and then I use the Bookends Safari bookmarklet to send it to Bookends. (Since it's the first bookmark on my list, I just click cmd+alt+1.) Then the usual thing within Bookends Browser: select reference and import it to Bookends. Sometimes do the same with the pdf as attachment.
– Open Alfred and search Crossref from it (the DOI of needed ref). Then follow the above sequence: safari > bookends browser > import.

- Go to Alfred (or LaunchBar...) and search Google Scholar or Crossref and open directly in the Bookends browser, skipping the Safari passage. (I know that we can do these searches via Bookends too, but it takes me longer and time is precious in a much used workflow.)

-- MJV