Okey. I have done a lot of experimenting. Since I thought, if the language layers can do so, why not my own custom layers?
Don't ask me why I did it, but it seems to work best this way. And I thought it would be good to share this with others.
1. Put the "Chat" layer above my "Gaming" layer.
2. On the "Chat" layer I put 2 conditions. When Counter-Strike:Source "is active" and...
3. ...second condition is "Lock keys" => Scroll"
4. On my "Gaming" layer I put the condition When Counter-Strike:Source "is active"
I did not manage to get my Y key to toggle the layer, but atleast my scroll lock will do that for me now. Whenever I want to see the "chat" layer instead, I will just toggle it back and forth with scroll lock. Whenever I quit Counter-Strike:Source, these layers will disappear and I will return back to my normal Windows layer
Maybe not the best solution, but it's a work-around for those who don't want to make advanced scripts/plugins.