How to remove empty workgroups from Branch Office list

We are standardizing on workgroup names and will eventually have only one workgroup per DC branch office.

I have noted that the remote office/workgroups combinations remain even after all PCs have been removed from the remote office/workgroup.

Is there a process to run on the server that deletes these unnecessary combinations?

See the attached file for an example of one branch office (Parmer) that has PCs with 3 different workgroups (see Capture.jpg - one workgroup shown in Capture2.JPG does not exist). If the PC Parmer57154-L is removed, how can I cleanup the pull down list for Parmer to show only the workgroups for AL-EXT and PARMER-EXT? See Capture2.jpg for current list.

MIke