Also make sure that you're not dragging from a scene reference if you're in a macro graph, because the drop target won't be enabled for scene refs.
I'm marking this as by design for now (because it's used to make headers smaller), but I might review that in the future. We're reconsidering inlined Unity Object references entirely for future alphas (because they come with a lot of constraints), so it's possible that those literals will go away entirely.
Bugs
It does have a drop target, only it's very small:
https://streamable.com/9zq1h
Also make sure that you're not dragging from a scene reference if you're in a macro graph, because the drop target won't be enabled for scene refs.
I'm marking this as by design for now (because it's used to make headers smaller), but I might review that in the future. We're reconsidering inlined Unity Object references entirely for future alphas (because they come with a lot of constraints), so it's possible that those literals will go away entirely.