Variables just hold a number.
You can create them under the 'variables' tab with the 'Create New Variable' button. You can also create variables by declaring them when using scripting. They exist separate to the pages, and you can use them in scripting or (more likely) making link restrictions (i.e. needing STR = 1 to pick a choice).
With that said, scripting doesn't need to be used, as mentioned you can make something where you just use variables and link restrictions (to have delayed consequences or stat based choices).
Also, under 'Storygame Properties' there is 'Editor Features', here you can click '[change editor features]' and crank everything up to the most complicated (that way you have access to everything). Doing this on a new storygame and trying to mess around with stuff might be a good idea. I know messing around in a test storygame helped me figure out some things.
Otherwise, most scripting articles are alright, and if something isn't well explained, you can ask a question in the advanced editor forums and someone should have an answer. I think if you've figured out the CoG system you should be able to figure this one out too.
The Price of Freedom: Innocence Lost is a CoG style game, you'll even see it has a stats page link! (Implementing new buttons is more complicated tho, but again, people can help with that).
You can see how it uses variables so that might help give you some idea of what you can do.
Dungeon Stompage! also shows some of what the editor can do, but making something at this level shouldn't be the goal for every story (but if your story requires it, it is possible!).
Koi Koi! is a more recent example that makes heavy use of the editor to create the game of Koi Koi, which is insane.
Suffice to say, you can have a choice 'do 1 push up' and have that increase the %STREGNTH variable by 1.