Trick is to check keybindings. Quicksave is F5 (F8 is quickload, which I removed from my keybindings to avoid using it by mistake).
I made a Steam guide listing controls and interactions which are really good to know before playing but that are not obvious at all !
https://steamcommunity.com/sharedfiles/filedetails/?id=2250219000( it is the top rated Steam guide for BG3 currently )
