Here's a link to some code to reproduce this issue: https://github.com/destari/macos-outlinegroup-bug

Switch the deployment target to 14.x and it should magically appear in your file navigator.

I have the same issue with Version 12.2 beta 2 (12B5025f).

Yea looks like Beta 7 and Xcode 12.2 have ripped it out for macOS. Sheesh. Release notes would be nice..