Super glue won't hold it for long if at all unfortunately. Desoldering is the only way. I do not know how much a replacement lcd selector would cost - maybe Mitsurugi or Darksoft can hook you up with a new one. Anyone in your local area that might be able to help you with the desoldering?
There's plenty of room to work around each leg of the buttons. Although it depends on if you have the right desoldering equipment but a simple solder sucker or desoldering braid and lots of flux should help. You can also add some new solder to each leg first to help. Try it on a leg without any...
I got a whole box full from amazon. I think I used either 6x6x14H or 6*6*15H, doesn't matter which one. Probably the taller the better so the button can reach out further from the case. My kit years ago came with a broken/snapped off up switch.
Hopefully you've this issue resolved by now, but if not:
Go here for the general info page http://www.codesrc.com/mediawiki/index.php?title=SCSI2SD
for version 5.0a firmware (latest should be 4.8.04) http://www.codesrc.com/files/scsi2sd/latest/
Your settings should be able to save after you...
I use version 5.0a from https://itead.cc/product/scsi2sd/. Upgraded the firmware to the latest and followed instructions from a few posts up. It worked for me. I am not sure about version 5.2 unfortunately.
My lcd selector is below, on the back I have marked in green the trace that is responsible for the select button. You can solder a wire between the two end points and the button should work.
Please verify your multi kit version before doing anything, but if it is the older kit then follow the PDF install instructions from there https://www.arcade-projects.com/threads/cps2-multikit-instructions-and-videos-old-version-till-10-2020.21/ and I think it starts at around page 10 of the...