Newbie question: how to create legend for percussion score

I'm a newbie working on my first score, a solo percussion piece. It uses a single staff, but it is not a drum set piece so the notation is non-standard and requires a legend to define it. I'd like to insert a short section of staff with the various notes labelled. It would not need any time signature, or even bar lines, and would precede the rest of the piece, which should start normally on the second line. Can anyone tell me if that's possible with musescore, and, if so, how do I go about it? Thanks in advance.