Grouped objects - Adding/Removing objects to a group

Hi.  I have a few objects that are grouped together.  If I want to add one to the group, I would think I could drag or cut and paste and object into that group?

I can't figure out how to add, or remove an object from a group other than ungrouping the whole group, making my changes, then re grouping the objects I want grouped.

Is there an easier way?  Thanks!