In Motion 3 the nudge 1 frame function does not work. The Apple Knowledge Base article says there is no workaround, but I have found that if you go to Motion/Commands/Customize and then duplicate the Standard set, rename it and re-edit in the nudge and move 1 frame commands using the keyboard, that nudge will now work as normal both in the canvas and the timeline.
Small thing but a pain in the butt not to have it work after you're used to having it.
Tom