this is definitely made in twine, I’ve seen this ui in a variety of twine games, it is essentially a default you can download for setting up games I believe, and is not far off from the actual default ui for twine (with some changes like the undo button being removed)
there's a bunch of tutorials for twine, a lot of documentation too. idk what's the best way to start, but id say checking r/twinegames is a pretty good, theres a lot of useful links there (mainly the discord was very useful to me)