The planner is a map, so the keys sit on the map. Press ? to open the sheet. The same key closes it. Escape closes it as well. Shortcuts do nothing while a search box, another field, or a dialog has focus, so Cmd-K search and typed names stay intact.
Z undoes the last point. Shift+Z or Y puts it back. R switches Direct and Low stops. U switches kilometres and miles. S cycles the map look when you are signed in. E expands or collapses the elevation chart.
Arrow keys pan. Space drops a point at the center of the current view, which is useful when you have already framed the corner you want. Delete removes the last point.
The sheet lists those same keys, so you do not have to memorize them before the first run. Open it, glance, and close it. The buttons on the map still do the same work if you never touch the keyboard.