Sure! Now you're stuck inside a certain catalog and you can only change it to another member of that catalog.
Having an extra field where you could actually pick another catalog, now that would be convenient.
Dropping a wall to a TF Linear Form, and a slab to a TF Slab Form won't really solve your problem if you can only add wall DG to Linear Forms and slab DG to Slab Forms.
I can't really think of a good reason why the delete from "dg modify data" shouldn't just remove the DG data, regardless of how that DG element was created. I'm not apologizing for it. It's not like it's my fault as far as I know.
Having an extra field where you could actually pick another catalog, now that would be convenient.
Dropping a wall to a TF Linear Form, and a slab to a TF Slab Form won't really solve your problem if you can only add wall DG to Linear Forms and slab DG to Slab Forms.
I can't really think of a good reason why the delete from "dg modify data" shouldn't just remove the DG data, regardless of how that DG element was created. I'm not apologizing for it. It's not like it's my fault as far as I know.