Just what the title says. Just like what VisualEditor does when you install it along with minerva.
The command $wgMinervaPageActions does nothing no matter how I modify it. Even emptying it does not change anything.
EDIT: I looked through the code and ended up finding what I wanted. I changed skins/MinervaNeue/includes/menu/PageActions/ToolbarBuilder.php line 175: 'edit' to 'tinymceedit'.
Would still prefer something official/better.