Is it possible to see a list of which games I have marked as "Not Interested"?
The "Excluded Products" for your account are listed at https://store.steampowered.com/account/notinterested/
- Go to http://store.steampowered.com/ (In your browser window NOT in steam.)
- Log In
- Go to http://store.steampowered.com/dynamicstore/userdata/ (refresh if blank)
- Look for "rgIgnoredApps"
- Look for the ID(s) to the Left of "rgIgnoredApps" Copy & Paste that id into this URL: store.steampowered.com/app/PUT_ID_HERE/
It's not possible to "Undo" them in bulk, however this should help make sure you haven't missed any along the way.
Following @Sriahciboon 's answer, I wrote a small python script that does most of the work for you. Here you go. :)
This requires you to edit the script and know a bit of python though.