Current questions and answers regarding the map editor.

Also: how do I make the player avatars visible in the game creation menu when selecting players? And why do all the settings revert after exiting the editor when I make changes in "player"?

Do you want the main heroes of the players to be visible in the game creation menu?
Then you need to open MapProperties --> Players Properties and iterate through the list of all players, setting the MainHero if necessary.