For once ADE has a reasonably discoverable feature: if you look under menu/Reading/Add Highlight it tells you the ctrl-M.
It would be good it they gave the hint on the right-click menu as well.
God, can't believe I didn't see it there, I feel stupid now . Thanks very much, you saved my day!
and yeah, the hint when right-clicking would be very useful. as i didn't see it, i asumed the worse (i.e. no shortcut)