You can change the vgps list from another tab. After adding the caches to the first list, middle click the vgps in the menu bar, (or long press if on a tablet) to open a new tap to the Progect-GC vgps page. Select the second list. Switch back to the original tab. The page will not know that you have changed vgps list, so will still show the original list, and caches will show that they have been added to that list. However that page is now operating on the second list. Remove the caches from the list (which of course does nothing, as they are not in the list at this point) then add them again.
They will now be present in both lists.