Hey, this looks cool and it caught my attention that you mention PDF annotation support. However, I see a Feb 24 commit labeled 'drop buggy annotation support' and can only assume that you ran into some challenges trying to go between Zotero and KOReader annotations? I'd love to hear what the challenges were and whether you think it's still viable to pursue - I'm trying to figure out and maybe develop a way to store and sync PDF/EPUB/HTML annotations across different apps (like some sort of universal file) and was planning to initially use KOReader's .sdr Lua file storage as the 'annotation file type' that other apps can read from (see
https://www.ryanwwest.com/pkm-annotation/ for a related post I wrote).