Now I'm not sure if the "next pane" concept refers to just that,
switching between left and right. Or if it actually should cycle through
the tabs that appear in the top row, which is what I want, as outlined
in the original post. That would be "notebook page" concept relevant to
the "notebook.set_current_page()" code, e.g. tabbing through 20
comparisons opened from a directory diff view.
I'm simply searching for a way to bind the Ctrl+Tab accelerator to
something like this pseudocode:
notebook.set_current_page(get_current_page()+1) # respectively -1