In the top right corner you have a search bar where you can type any name from any rule, table or anything in your application and can be found. If you don't remember exactly the name, just press "enter" without entering nothing and you will see you application structure.

Hope you can find it, if not make sure you are in the right application (click application menu and then on switch application and verify your application is selected)

You can see exposed column Database structure using Designer Studio -> System -> Database -> Modify Schema.

You first need to know what Schema and database table to view.

You can also see what columns could potentially be exposed according to Properties flagged as "column inclusion = Required" according to their Advanced tab.