For repeating the previous action I use a button from the edit menu and have it placed on my layers palette for easy access. I find it an easy way to repeat an action especially when adding shadows and on the layers palette it is very handy. I only use a mouse and I have to use 2 hands for Ctrl Y .. this way I don’t have to leave the mouse.
If you want to add it to your task bar or layers palette, go to view, customize and under commands select edit (on left under categories heading) and on the right under Commands it should be 3rd icon down, then simply drag the icon to your task bar or the layers palette.
I have several of my most used icons added to the task bar in this way.
Hope this is ok to post Carole.