Is it possible? I can only seem to find a horizontal split view, which seems a bit pointless considering monitors are never taller than they are wide

no afaiak. you could press F10 for the code window and resize it to the side of the main window (you could float it over the panels on the right if you make those panels say 1/3 of a screen wide.

some monitors ARE taller than wider e.g.newspaper offices sometimes use those models that you can turn either way

Ah thanks, F10 it is then! I'm still surprised that Macromedia decided to only include a horizontal split view arghhhhhh!