So Blender 2.7x or 2.8x added a feature called "Global Undo". This appears to have hosed the ability to undo and redo palette modifications for me. It is really easy to trash your palette!
If this is affecting you, you can do one of two things:
1) Enable "Undo Legacy" from the Experimental tab in preferences.
OR
2) Disable "Global Undo" from the System tab in preferences.
Perhaps you can do both at once? But either or should work.
Blender 2.7x or 2.8x added a feature called "Global Undo"
This is not correct; Global Undo is a lot older (the oldest Version I have on my computer is 2.63 and that already has Global Undo).
Undo Legacy was introduced when the new Undo system was added (2.82 or 2.83, I think), because the 'old' undo was very slow (but more stable in some cases).
I would not recommend disabling Global Undo. (But of course you can do whatever works for you.)
