@unopenedparachute . In your screenshot, you’re showing the ‘post background’ setting. There’s another, if you scroll down, called ‘post area background’. That may be the one you’re still missing.
I just noticed we’re on different dialogs, so it may not appear where you’re looking.
But you seem to have it figured out. It’s just a matter of finding the settings, which are a bit scattered. Good luck.