Exchange state types in a state diagram

Hello,

First off, thanks a lot for providing such a great tool for free!

I'm just getting started with UML. I'm trying to do some state charts,
rather with Argo than with Visio this time :)  But I have a few problems,
and I don't know whether I'm doing things right. This is with v0.24.

There are simple states, composite states and substates. During design,
often a simple state becomes a composite state or a substate. Is there a
way to make a simple state a composite state or a substate, without
deleting and subsequently recreating the state and all its transitions?

Since I didn't find a way to do this, I tried at least to preserve the
already created transitions, by creating a new state and moving the
transition endpoints from the old state to the new state. I also didn't
find a way to do this. When I drag an endpoint to a different state, it
just snaps right back to where it was. I also don't see a way to edit the
Source and Target fields in the Properties.

Both (changing a simple state to a substate and moving the endpoint of a
transition) seem to be very common needs during the design of state
diagrams, so I'm almost sure I'm missing something here. Can someone please
help me out with this?

Thanks,
Gerhard