It sounds like you are referring to tracks within a Folder, not an Edit Group. Is that right?
In other words, you Packed a set of tracks and now you want one or more of them outside of the Folder.
If that is the case, you just click and drag the track(s) to a location outside of that Folder.
If you really are referring to an edit Group, the verb is Dissolve if you want to Group to just go away.
If you want to change Group membership, double-click on the group name. That will highlight all of its members below.
Select and right click on those you wish to remove from the group and choose "Group Assignment".
Uncheck the box.
