change active frame (column or pane
It took years to find out that with F6 I can change the active column in most programmes. Examples: In nautilus, I can switch between the left and the right column, in evolution (classical view) I can cycle through the three parts of the window - post boxes column left / message list top right / message body bottom right.
This is a good feature - by why is it activated by F6??? - This is really an unhandy key and not suitable for such a regularly used feature. And I cannot even change it (maybe someone else can and tell me how?). The TAB key (and Shift-TAB for the reverse direction) would be nice - such it's done in Mac OS.
And the other thing: No highlighting is given for the active frame. MacOS does so, and it's really essential for efficient keyboard navigation. I still miss it after many years now on GNOME.