Keyswitches in Score

How do I prevent keyswitches from showing as notes in the score?

This is in an imported MIDI file?

If you need them to still play back, I would suggest adding another player to your project with a duplicate instrument for the one containing the keyswitches, then move the keyswitch notes from the original instrument to the new one. Exclude the new instrument from the full score for printing and from the instrumental part, but include it in one of the layouts (e.g. make a new full score containing all players and instruments called ‘Playback Score’ or similar). Then in Play mode make sure that the newly-added instrument to which you’ve moved the keyswitches is set to play back through the same VST instrument and on the same channel as the original instrument.

You could use Playing Techniques that trigger the MIDI events instead.