I like to set Ctrl-§ as the shortcut for moving to the workspace left of the
current one. I do that by going to Settings -> Window manager in the XFCE
menu, going to the Keyboard tab, scrolling down to the Left workspace action,
double-clicking it, and hitting Ctrl-§ to set that as the keyboard shortcut.
This takes effect immediately and works throughout the login session, even if
the shortcut will be listed in the action list as 'Primary + Section' rather
than 'Ctrl + §'.

However, if I reboot the computer and log back in this particular keyboard
shortcut no longer works, though all the others seem to work. When I go back
to the WM keyboard settings the shortcut for the Left workspace action is
still listed as 'Primary + Section', and if I double-click it and hit Ctrl-§
it stays listed as the same, but now it will go to the left workspace when I
hit Ctrl-§ again. For some reason this configuration does not survive logouts,
which I would expect it to do.