There are a number of issues with Composite State Regions:

• Creating a Composite State adds a default, unnamed Region (nice). However, this region does not resize when resizing the State shape (very annoying: have to resize BOTH region AND state each time something changes)

• Even if above behavior is intentional (e.g. to allow partial displaying of a region by setting the size of the enclosing State smaller) then provide a means to "autosize" and/or "lock" the size of the region to the enclosing State. It seems that the height of the region is a property of the model element, not the diagram element, which seems a bit weird. Even if that is necessary, locking the last region to the enclosing state element would be a very much appreciated feature and save me from continuous frustration when resizing States. This works also in the case the State has multiple (orthogonal) regions: the size of the last region (and only the last) is not user defined but calculated each time the state is resized.

• Regions can be added to States in the model explorer. However, such a Region is basically useless (kind of orphaned) as it is (i) not added to existing diagrams and (ii) there is not even a way to add them manually! Even if the State is (iii) removed from diagram and added back, or (iv) added to a new diagram, such a region is never displayed!

• continuous default naming of regions (Region1, Region2, ...) is wrong. Regions added on diagram vs. Regions added in model explorer get the same sequence number

• substates in a region appear below the region even if the position of the substate is outside the region boundary (i.e. region smaller than substate position).

• substates in region 2 of a state appear to be in region 1 if region 1 is enlarged (instead of shifting position while region is resized)

There may be other issues. It seems that the metamodel is wrong ("diagram regions" and "model regions" are separated and not synchronized properly in all cases)