Modifying object type in Data modeler destroys inner classes

Description of problem:
I can have a class with inner class or enum modelled outside Business Central. When this is pushed into BC it can be further modified using Data modeler (e.g. adding a field, adding label). When the changes are saved the class is re-generated by Data modeler ignoring inner classes.

Version-Release number of selected component (if applicable):
CR2

How reproducible:

Steps to Reproduce:
1.
2.
3.

Actual results:
Inner classes and enums are dropped.

Expected results:
They should be preserved.

Additional info: