If you’re using a custom drag and drop operation, you can do it there:
Since we’re not dropping on a widget, and there’s no return confirming successful completion, this cancellation will trigger inside the operation blueprint.
If you’re going to use this method for a variety of classes (assuming there will be more than just chairs), you will also need to look into either inheritance and / or interface communication. Casting is not sustainable. But that’s for later.
Or use a channel for tracing, then you no longer need to worry about enabling / disabling collision. Both would work but require a slightly different approach.