Hey! I added some of your feedback in the latest release https://danielgriffiths.itch.io/rhythmrune/devlog/1005496/-update-v12-high-score...
Difficulty will be added at a later date, I need to go through each song and figure out how hard they are.
No worries! I actually just pushed another update (added to the existing 1.2 change log).
There was an issue where if you tried to load a song that didn't already have a notes.chart file that you would get a blank screen, which means you could edit songs but not easily create new ones.
This should be fixed now, I only have access to a Mac atm so have not been able to test this fix on Windows yet, but hopefully it fixes it there too.