I can’t remember if standard fold commands worked prior to live preview but I have to map za to toggle fold, etc. using esm7/obsidian-vimrc-support: A plugin for the Obsidian.md note-taking software (github.com).
exmap unfoldall obcommand editor:unfold-all
nmap zR :unfoldall
exmap foldall obcommand editor:fold-all
nmap zM :foldall
exmap foldtoggle obcommand editor:toggle-fold
nmap za :foldtoggle