Hi Marc,

re:
> It would be nice to have a way to open and isolate a group, perhaps by double clicking ?
> Other object could be grayed out.

There is a "Lock" function that works like this currently, if you select the group you can right click on the Edit > Lock button to do a "Lock isolate" which will gray out the other objects and prevent them from being selectable like you are describing.

When you're done you can do another right click on Edit > Lock to restore things back to the pre-isolate state.

You can also right click on Edit > Hide to do a similar isolate but where it hides the unselected objects instead of locking them.

- Michael