I think that PianoBooster is a great program for piano learning and strange to see it not actively dveloped.
I thought that it would be great for piano learning to have in PianoBooster the option of automatically generating a stream of accords according to some parameters: key, temp, intervals, the number of notes in accords etc.
I added preliminary code for this feature to the program code and currently am debugging it. If there are some developers who still work on PianoBooster I could upload the code to github. So that if this functionality is interesting it could be improved and maybe included in the next version.