Is there anywat I can undo "add to shape area" effect.
I am not talking about the case where I can go back with step backward.
I am talking the case where I have saved my work, closed Ps, reopen it, and then undoing the "add to shape area" effect.
Depends on the shapes vector mask. If there are subpaths or have they been combined into a single path.
Here are some screen captures that shows this. I've use CS5 for it works better then CS6 and the old layers palette showm shape layers vector mask where CS6 only shows a icon indicating its a shape layer. You can edit the shape layers vector mask in CS6 but I feel CS5 screen captures show what is going on better then CS6 screen captures.
Capture 1 Shows Green shape Layer
Capture Two Vector Layer mask targeted and Path Selectool use to select a subpath
Capture three that subpath delete an other also selected and deleted
CS6 Layers Palette Shape layer
You can still select and edit subpath if the exist
But if they have been merged you will not know it till you try to edit the shaps path for there is single path
Just select the individual subPathItems with the with the Pen Tool (command-alt-click to select all pathPoints) or Direct Selection Tool and change their Shape Operations in the Options Bar or delete them.
From your screen capture it looks like your vector mask has subpath so you can select and edit the subpaths. You would not be able to see this in the CS6 layers palette even if you forced CS6 to Display Vector masks in the layers palette for some reason it does not show subpath in the layers palette. You would need to try to edit the vector mask to find out or additionaly show the Paths Palette.