I made some working examples, but I found a bug, I cannot solve:
If I have a containercontrol which accepts textdrop and which has a weblabel inside, the drop-events just work correctly if I let drop my drop-item in a free space of the containercontrol. If I let drop the drop-item onto the weblabel, which is not allowed to accept drops, I get a Event-Loop exception.
Perhaps Xojo didn’t test dropping directly on to the WebLabel - I can get the Event Loop lock behavior.
I did not get the behavior until I came back, re-read, and very specifically tried to drop in the right spot.