I don't know if this has been requested (or if it is already there and I just hadn't discover it), but it would be great if GMedit supported creation, editing and auto-complete of  the "variable definitions" feature of GameMaker. Even in a non-graphical way where the user would define variable_name/type/value would be great.

I had been thinking of it time to time but I'm yet to come up with an idea of code representation of variable declarations that doesn't look horrible for multi-select variable types

Thanks for the reply!

I guess you mean about the list type when multi-select is checked? Yes that seems it would be a problem. If you allow me to make a suggestion:

#def variable_name
type = list
multi_select = true;
value = {
    "item1" : true,
    "item2" : true,
    "item3" : false,
    "item4" : true
}

#def variable_name
type = string;
value = "hey";

I would need to think more about a clean way to edit them, but I'll say that this is a feature I would love to have. I was happy to discover variable defs. They're a great feature that make level creation a lot nicer. I'm almost free of having to deal with the GMS2 workspace, except for having to add them through their bulky editor, and not having them show up in GMEdit code completion.