If you go to the last tab in Design, it's there. If there are none left, you've fully expanded.
If you want to expand, you may have arrows at the end of the screen, you can click these and it will show what your next expanison is. You can also look in your design tab and there is an expansion section . It will tell you expansions to unlock and how many nbr you need and how many coins. You may also have an option to expand early if you buy with gems.
Nightclub Owner