View attachment 93819
If you're just talking about the vertical layout, either right-click the empty area in the mixer or click any of the 3-dots buttons for a source:
View attachment 93820
Does another app use them okay?
Yep, all other apps (iTunes, YouTube in Chrome or Mozilla, email notifications, etc) are fine, and here's the really strange bit. IT'S WORKING TODAY. I close OBS completely every time I am done with it, so I am 99.9% sure I've closed it since I changed to Monitor and Output, but when I opened it just now to run a system update so I'd be ready for Tears of the Kingdom, I could hear the audio via my onboard speakers and my BT headset. I have zero clue why it is working now, but I also don't care, apparently it just wanted to make me wait.
Shamless Plug time - next Friday (12 May) will be streaming TOTK as soon as I'm able. I still don't know if it'll be on YouTube (Old Man With A Switch, find Sheepdog Smokey, it's a picture of me as twins in front of the Tx flag as the icon) and go to Channels to find OMWAS, or on Twitch as SheepdogSmokey, but I'll post to the one I'm not going to use that it's the other once I decide. I'm in a meeting in about 5 minutes, but after that I'm planning to test both to see which I prefer.