You can try this semitone script.
zaibuyidao_Insert Pitch Bend (Semitone) .lua -- Inserts a pitch bend, with a value ranging from -12 to 12. Enter 1 to get a pitch bend value of 683, Enter 2 to get a pitch bend value of 1366, and so on.
You can download it here:
https://github.com/zaibuyidao/ReaScripts
Or add a repository from ReaPack:
https://github.com/zaibuyidao/ReaScr...ster/index.xml