Simple menu, better as list, not “squares”. Menu must contain tunes that was ever downloaded and saved for all cars. Same for designs.
There’s a limit for saved tunes in FH series, internet says that this limit is 500 for tunes and designs.
To delete saved tunes player need to change car, open saved tunes for this car and only then delete. Additional trouble added by very unfriendly car UI, it’s too big for such amount of cars, and there’s no way to see if tune was ever installed for car, only by rank(like 600, 700, 800, 900).
Every active player will get to this at some time.