I've just recently learned about Zettlr and I'm starting to quite like. I was looking for answers to a different question and have stumbled upon this thread. I've been using Logseq for some time already, which I also like a lot, but I'm getting the feeling that I might want to move to Zettlr or perhaps use both.
Anyways, I'm telling you guys all this, because Logseq integrates AI at any point you want, whether a daily log, a dedicated page, etc., very easily and it works quite nicely. Perhaps their implementation could be of help or inspiration to add that functionality to Zettlr. As I understand it, they have implemented as a plug-in which adds functionality in a modular fashion.
As I said, I'm very new to Zettlr, but I've thought that this info could help somehow...