At some point you may want to create your own lead sheets. Especially if you’re doing your own reharmonization and your notation gets crowded out on your standard lead sheet – or if you’re trying to harmonize a song by ear. (I have some interesting – at least to me – variations of traditional Christmas carols, as an example.)
There’s a great app called MuseScore that you can get here. It can be installed on virtually any operating system and can be connected via your MIDI keyboard should you have one. The learning curve can be a little steep but the program is very clever and there’s a format specifically for lead sheets. I’d suggest using their browser-based help resources when you start. Later the app-based help may be sufficient.
As an aside, if you have a song you’d like to voice but don’t have a starting point, here’s one possible way of getting started. Work out the melody starting from whatever note you’d like. Once you have it mostly figured out (or maybe you have a score without chords) figure out what key you’re most likely in. Then you can peruse your fake books for a song you may be familiar with in the same key (or transpose your melody). Using the chord changes from the song you know, you can get a start on voicing the song yourself.
It’s not always that simple (which is why I started with Christmas carols) but it’s a beginning. If you’re an Advanced Member, review David’s info on chord substitutions. Experiment and have fun. Break whatever rules you feel like. Share your success stories.