Probably not a bad idea to start the list, however Khaled stated the best move would be to start an online wiki, which already exists and also has tutorial on all scripting features: https://en.wikichip.org/wiki/mirc
All commands are documented (except for /ialfill) but only half of identifiers are.

#mircscripting @ irc.swiftirc.net == the best mIRC help channel