How to assign note heads without doing them individually?

Yes so, I came across this score:
https://musescore.com/user/32123243/scores/6629096

And at first I thought well maybe the user did it manually one by one, but when I went to to transpose it, I noticed that the notehead letters changed as well - so It definitely wasn't done one by one. So how would I be able to assign that feature to my note heads? I know of the note name plug in but how would I be able to do that with the note heads?

Thank you in advance
-Raquel