Marbux wrote:

I have used Diigo for several years but hate it. It is vendor lock-in
software. Its API does not permit exporting of all your data. I took a
very hard look at using its API to move data back and forth between
NoteCase Pro using NC Pro's scripting capabilities, but was completely
blocked by Diigo's API. You can get some but not all data types out and
the ability to restore it after processing in NC Pro is non-existent.

In my mind, that fact weighs very heavily against Diigo's convenience of
use. I was seduced by that convenience but am now making the transition
back to Zotero. I don't think there is another digital research
assistant out there that comes close. Yes, it has a steep learning
curve, but it is an extremely versatile system so that's to be expected.
Take a look at the quick-start guide if you're interested.
https://www.zotero.org/support/quick_start_guide

The Zotero system is open source software and the API is mature. And no
vendor lock-in in sight.

Marbux, does Zotero allow you to clip just one sentence or paragraph from a PDF or webpage and put just that sentence or paragraph into an outline or list? That functionality is pretty key for me and I don't seem to see it in the initial Zotero documentation. For instance, I want to have an outline of all the definitions of a particular term that I've found on the web or in literature. I don't want the outline to include the entire documents - just the definitions. But I want the definitions to have citations (and ideally hyperlinks) back to the full document. I can do that with Diigo - albeit clumsily - using the "convert annotations to bullet points" feature. But I share your concersn about Diigo and would switch to Zotero if it supports this functionality.