cereberus said:
The odd thing is mine did too initially but when I removed sandbox , the portablebaselayer disappeared, and when I reenabled sandbox, it remained hidden.

Try it.
Tried it. Disabled Hyper-V and sandbox - rebooted and re-enabled etc. No porteblebaselayer showing in Disk management.
With sandbox running shows 5% usage in MiniTool. Hey-Ho.
Enable or Disable Reserved Storage in Windows 10-screenshot_2.png