I'm sure this has been done before. I took my most used or hard to remember X3 shortcuts and put them in a Sonar wallpaper bmp. After you load it, just minimize your project to see it. I mostly use midi so the info is midi heavy.
Anyone is welcome to download it here:
download It's 1920 x 1080 resolution.
If you've never changed your wallpaper: Edit -> Preferences - Colors, Click on the Custom button at the bottom of the window and navigate to your wallpaper file. To reload it, click the None button then click the Custom button again.