I just solved this after hours of stabbing in the dark, hopefully this helps everyone that has been lost by this. Here is the example workflow to transfer a thing (in this case equipment) from one list to the next.
Background: I have a RG of pickable equipment with a draggable group in each cell of type equipment, the ‘DropArea Equipment’ is of type equipment as well, this has an empty data source. I have a page ‘dev’ with a custom state ‘temp equip’. The workflow uses an identifier I’d never seen before “current workflow [thing]” that’s the secret to making this flow work. You have to set the workflow to reference the item in the DropArea action using that call.