This is a Quick Start Video but if you want to clear a locomotive from one of the selections. Turn on the power your Universal Remote. Press and hold the Engine Selection Button you wish to clear.
Once the button begins flashing rapidly, release it. Repeat this process with any other Engine Selection Buttons you want to clear.
Re-watch these frames in the video, 1:43 to 3:57
Check out illustration below or the YT video description.
Gary