Allow melodic ideas to be saved in some sort of "pocket" that doesn't change the score

(Note: I am an absolute beginner)

I believe that it would be very handy if melodic ideas could be saved somewhere easily accessible within a project without being on the score itself. When an idea comes, one could just quickly mark it up in something akin to a note or the application notepad, but in musical form that can be played back in the program.