On the '15's you hold down the right knob for a couple of seconds, and do the same to go back. There was also a way to default it in the settings. I haven't looked at the '18's so I don't know if the knob is still there!
I've not been able to find that, either. Nor can I change the background. And the cool vehicle monitor tools aren't as cool, although the pitch thing is neat. I miss the live acceleration monitor. My wife's 2018 Forester has a really cool wheel diagram that shows which way the wheels are turned and the wheel spin for each wheel. Don't think the OB 2018 has that.