I mean, the payload is the data. What are you going to do with this:
Soon, you will need to detect what happens when drag enters a slot. Now what?
Again, this is not set up correctly. A slot should hold a widget that represents the ability. What is this data even doing inside the slot:
Slots should not care about any of this, slots just hold ability widgets and move those widgets around. This way the re-parenting is done completely automatically and you never worry about the things that you’re worry about in the original message. The root of the issue that this is not drag & drop at this point.