There's also a few more, but I don't know how usable they are.
The entire history stack can be accessed with ID numbers.
Basically if the history stack was something like:
Undo New Composition
Undo New Layer
Undo Change Value
-------------------------------
Redo Parent
Redo Add Shape Layer
Then the IDs would be:
Undo New Composition : -1048577
Undo New Layer: -1048578
Undo Change Value 16
-------------------------------
Redo Parent 2035
Redo Add Shape Layer -1048582
Redo Add Camera Layer -1048583
The stack always starts at -1048577 and then counts downward by 1 (skipping over 3 numbers when Undo changes to Redo)