Undo Manager does not record my Color Transparency clicks. It records other actions, making layers, Clone Tool, but not the Color Transparency Tool. When I do some individual clicks with Color Transparency Tool and I make a mistake, I hit Undo and it zeros out everything I did. I know you must do individual clicks (let go of mouse) for actions to be recorded. I think it's a bug with Undo and Color Transparency Tool.
Not a bad idea, I think an oversight in design not a bug.
I decided to check this on my system and the undo manager records every step and change in transparency.
Maybe you can show a vid of your procedures.
I get days and then I have more days, glad it works now.