Expose Interface - cannot add used interface to a class

[David Hagood]

I am trying to model a case where a code generated class (containing a state machine) will be provided access to an external class that implements a specific interface. That external class will be hand-written. Then, when things are deployed, an instance of the external class will be created, and connected to the generated code.
Exactly what provides and uses interfaces are for.
Making my hand-written class expose the interface as a provides is easy - define the interface, define the class to be written, mark it as realizing the interface, done.
However, I cannot get the tool to allow me to drop a uses interface on my code generated class. Dropping the "expose interface" on the class is supposed to give me a dialog to choose uses or provides, and set the other parameters, but I don't get that dialog; it just drops a provides interface on the class with defaulted parameters, as though the dialog is being closed.
This is running on Linux under Wine 6.5  - could there be an issue with the dialog in such a case?