If I understood correctly, you could use File->import-> Simulation entities, to import Groups from another sim file.
That's one way but this option will import all the groups. So groups could end being duplicated Easy enough to import all the groups then delete the ones not wanted.
What if one wants to import specific groups?
In my problem description I used the .sim file as an example but I'd like to do that with a .fem (.or afm). In other words being able to export any groups I want from a .sim/.fem/afm and import them in .sim/.fem/afm. I am only thinking about element and nodes at the moment.