In Group-By Panes, dragging between groups should modify the dragged item so that it is included in the dropped-in group. In G-B Tags Panes, dragging an item with one #tag1 to a different #tag2 group replaces the #tag1 with #tag2, and the item disappears from #tagt1 group and appears in #tag2 group. If there are multiple #tags on the item to start with, the destination #tag simply gets appended and the item appears in all relevant groups. This behavior is consistent, predictable, and useful.
But it doesn’t work with +Contacts. Drag/Drop has zero effect in a G-B Contacts Pane.
Drag/Drop between groups should work the same for both #Tags and +Contacts.
