How do you edit a virtual group (add/delete groups)

[<jari.aalto@poboxes.com>]

    How do I know what groups I have included in the virtual group? I
    can add groups there with G v but what if I want to add new groups
    and delete/move some other groups to other virtual groups.

    I'd like to see some sort of "edit" mode added to virtual groups, where
    edit buffer would look something like this:

        Virtual group A
           group1
           group2
        Virtual group B
            group1
            group3


    you could a) add new groups b) kill groups from virtual groups
    c) move/copy groups between virtual groups.

    But right now it'd suffice if there were at least some G X to edit
    current groups included in one virtual group, so that I could kill or
    peek what groups were in there.

    jari