A few suggestions for Unity/Trombackgrounds:

[Guarde]

Just a few things that I thought useful when I created custom charts.
I have no idea how viable some of these are but ill write them down anyway.

A couple suggestions for new events:

• Champ meter on
• Champ meter off
• Trombone On Event (could pass pitch, triggers once)
• Trombone Held Event (could pass pitch, triggers every frame/timestep while note is held)
• Trombone Off Event (could pass pitch, triggers once)
• Note precision events for Nasty/Meh/Ok/Nice/Perfecto
• Score Updated Event (Passes score)
• Lyric event (for animating faces)
• Have the NoteStart() and NoteEnd() events pass a pitch (or maybe a duration)
  Edit:
• Cursor Position Updated (Track the position of the dot, rather than the mouse to accommodate for AutoToot; Passes Vector2)

Other nice things:

• A simple 2-part If-This-Then-That logic script.
  • Has a function that can be used in triggers to pass values to the script
    (e.g.: if combo == 10 -> fire event)
• A function to fade the Gameplay UI in or out, rather than having to slap a render texture over it
• A function (or prefab) to translate the mouse position to a rotation with the set boundaries
  • Useful to tilt a character's head or body up/down without a needlessly complex setup of parent constraints and look-at constraints
• A way to apply the projects lighting settings (skybox, fog, skylight...) to the project. maybe via a "UseCustomLighting" gameobject, similar to AddShadows and RemoveDefaultLights (I would love to be able to use fog!)
• A way to test TromboneEvents within unity (like NoteStart, NoteEnd, etc....)

Notes:

• The OnBeat()-event, actually fires every bar instead of every beat. Fixing it would probably break some backgrounds though