Okay, so I went and looked at Chrome Music Lab so I could see what you're working with. It seems like you only have one real instrument and a couple of drums. So this was a real challenge, nice attempt. One thing you can do is make different lines with different note 'lengths' to treat them like different instruments and mostly lock each of them to one scale. Without getting into theory, you can also save and go into chromatic mode and try lowering all of the notes of one color in a section by one. Here's something I put together as an example using arpeggiated chords in the base:
https://musiclab.chromeexperiments.com/Song-Maker/song/4979951897542656
What I'd really recommend if you want to go a bit deeper, without jumping off into DAWs like LMMS, or FL, is to try out Bosca Ceoil. It's free and even available on Steam.