Technology truly is a gift when it comes to composing at the piano. From automatically notating what you play to turning hand drawn notes instantly into professional notation ready to print, here are some programs I use frequently in the studio.
With a simple printer cable and a digital piano or keyboard (or the keyboard in the app itself), Notion transcribes whatever notes you play. You can add whatever clefs, instruments, dynamics, etc that you want and as soon as you stop playing it is ready to print out! It will also play back your score for you. It feels miraculous!
NicoNotes is well-suited for introducing my youngest pianists to creating their own melodies. They can put songs on a staff for multiple instruments and hear/watch it performed back to them!