More recent updates of Trombone Champ have added songs with variable beats per minute. The game does seem to have some sort of special behaviour for these tracks, where it hides the beat bars after a specific point in the track, although I'm unsure of if there's anything else going on in regards to how the data is actually stored/read, so actual functionality for custom charts may be limited.
At the very least, being able to hide the beat bars would be better than no variable BPM support at all.
More recent updates of Trombone Champ have added songs with variable beats per minute. The game does seem to have some sort of special behaviour for these tracks, where it hides the beat bars after a specific point in the track, although I'm unsure of if there's anything else going on in regards to how the data is actually stored/read, so actual functionality for custom charts may be limited.
At the very least, being able to hide the beat bars would be better than no variable BPM support at all.