Create a layout with two tiles and multiple tabs in each.
Make sure the focus is in the left-most tab.
Click on one of the tabs in the right-most tile which is behind, to bring it to the foreground.
Immediately press Ctrl+G.
The focus goes to the Reference box in the top tab of left-hand tile. It should go to the Reference box of the tab you just clicked on. The latter should be activated as the one with the focus.