I use DEVONthink’s “artificial intelligence” suggestion skills when writing. Occasionally it does not seem to be as “intelligent” as it should be, when it makes suggestions based on words that I happened to overuse in a note but that were irrelevant to the subject of the note. But usually it is good at pointing out relevant information in my reference material and in my own past writing.
In addition to the shorter notes in my Zettelkasten-like personal hypertext system, I also sync my longer-form writing projects from Scrivener to an external folder and then index that external folder in DEVONthink. So if I want to find material related to some part of a Scrivener project that I am working on, I open that part in DEVONthink and hit the “See also” button and it shows me related material, often material that I had forgotten.
It helps to have information stored in relatively small chunks (a few paragraphs, not whole e-books), so that the “granularity” of the “See also” results is accordingly small.
The AI suggestions have become more helpful as I have accumulated more information over the years, which is so much more material to forget.