UI - Add Custom Orientations to Orientation Pie Menu

The orientation pie menu is extremly useful to quickly change between global, local, normal, etc.

But if you have some specific angle you saved as a custom orientation, it's never added to that pie menu so it becomes chunky changing from one to another. There's a convenient empty space in the pie menu where custom orientations could live, I would suggest by pinning in the UI list, or perhaps a list.

Here is a mockup: