Set up two vertical grid-panes.

This next bit is not important - but for the sake of example have a couple of tabs open in one pane.

 

Navigating using Ctrl+PgeUp/PgdDn works only until you get to the end of the group of tabs - then it opens the manage grids dialogue.

 

I havent used this in a while (need a lot of grid-tabs open currently so back using it again).

IIRC, here's how it used to work:

when you reached the end of one tab group, it simply moved from one pane to the next (when using the keyboard combo).

 

Hope that all makes sense

Tom