Yes, you would want to put that in your character somewhere. In theory you could put it in the Ability Task Tick - but that’s a bit heavy IMO. I would just make a gameplay tag called, “AbilityCancelOnMovement” and when your Ability plays, add that tag to the character. In the Character’s Tick (which has to run anyway) - check if the Player is playing an Ability, and if that Ability has that tag - if so and the player is moving, simply cancel the Ability.
I go into that in the latest video a bit. https://www.youtube.com/watch?v=fOJ0WR9B75E Those are “Dynamic Bindings” which allow you to swap the value of that field at runtime. They’re called automatically by Able under the hood. In theory, since their just BP functions, you could call them - but only by the Ability’s own blueprint, not by anyone else.
With regard to the Blueprint Library, I can’t really say. I haven’t had a lot of time to dig into it yet. If you open up the Ability Blueprint and just filter methods by “library” - you’ll see quite a few methods (I get Oculus and a few other VR items). Looks like a normal Blueprint function library under the hood, BlueprintPure / BlueprintCallable both seem to work. You might want to make sure you setup a proper category so you can find things directly “MyFunctionLibrary|MyFunction”. But, that’s all I can offer at the moment. I can look once this update is out and my plate thins a bit.