When the left Trim Handle is active, pressing [Tab] or [Enter] switches to the right handle.

If you pressed [Tab] or [Enter] to make the Trim Handles or Scrubber active, use the Left-arrow key to move to the previous frame.

If you pressed [Tab] or [Enter] to make the Trim Handles or Scrubber active, use the Right-arrow key to move to the next frame.

If you pressed [Tab] or [Enter] to activate and toggle between the Trim Handles and Scrubber, you can press [Esc] to deactivate the Trim Handles / Scrubber.