I don't think the editor will ever work with a controller. You need to do some typing to get stuff working (dialogs, scripts, names, settings). It's an editor like a dev uses, so the modders have all the power, i.e. it's not an editor that a six-year-old can use. (It's not a "Shoot Em Up Construction Kit" type of application, it's a full blown RPG editor. Not a commercial "Make your own RPG for dummies" thing.)
A good isometric RPG with controller support ? Maybe yes, but certainly NOT Divinity : Original Sin !!
That's now cristal clear to me !
And I'm wondering why the h**ll this question was coming up