Hi Benjamin
It is possible to 'join/leave' groups in SwyxWare, but not in the way you think. The member will not be removed from the group itself or added. You achieve this by configuring the Lines key in SwyxIt! (or SwyxWare Administration) and it will work on SwyxPhones also. Configure a line key to only accept call from a specific group. It is important to have a couple of lines available for calls directly to the user also.
Right click on a line key in Swyxit! and select Properties, then configure the incoming calls. If you want to leave/join all groups on the same line you can choose: Only group calls.
When you want to 'leave' the group, just disable the corresponding line. In SwyxIt!, right click on the line and disable it. On SwyxPhones you hold down the line key for a certain period and disable it, the line key will flash while deactived.
There is one huge sideeffect of implementing leave/join of groups in this manner. The user needs a phone that supports the line configuration. That is only SwyxIt! and SwyxPhones. SIP and H.323 devices will not be able to leave/join groups.