Hi, there, I am also a fan of Zotero, stopped using Endnote as it had major problems on my Macs, and then I discovered Zotero, that is an amazing solution and I wish I knew earlier. Have been using for over a year now. Everything works great but I also started having similar problem recently. I am writing a doctoral thesis that has really many citations(hundreds and hundreds (if not thousand) of references cited multiple times each). Every time I insert a citation in Word, I need to wait a lot and when I say a lot I mean over 5-7 seconds and this delays my work. I can't identify when it started to become slow, but I also assume its after a certain threshold number of citations, as in the beginning of my writing it was working perfect. What can I do to fix it? And how can I find this setting of "keep sources sorted" and "quick format"? As I can't find it anywhere.
https://www.zotero.org/blog/zotero-5-0-36/#faster-citing-in-large-documents