I found the MMU3 buttons a little hard to push and the existing solutions were too loose in the button holes and ended up partially turned so I made my own extensions.

Delete the "_Let" parts if you'd prefer a debossed button.

I've found the buttons to work in either orientation (long flange up or down) depending on preference of viewing angle - I actually prefer long side down.

A couple folks have had issues with the buttons being too tight a fit so I added some smaller options in the “Trimmed Parts for fit issues” folder.  The larger the “offset” the smaller the button for these, 0p1 (0.1mm) is the standard and they get progressively smaller from 0p2 → 0p4.