Is it possible to merge multiple gnome-terminal windows into a single tabbed view? [duplicate]
There may be another, easier way to do this. But what I've found to work, is to activate the tab-bar in both terminal windows by pressing
ctrl + shift + t
and dragging the proper tab into one of the gnome-terminal windows. Then close the empty tabs until you are left with a single view.
Illustration
Drag the tab into the other windows tab-group
Once you have 3 open terminal tabs in a single view, close the extra, blank, terminal tab/window and you have achieved the desired result.