Notice that Tall takes 3 parameters, but you're then using it again without any parameters under control of Mirror.  The error message is complaining about the missing parameters; this tends to look a bit odd in Haskell, because sometimes that's an entirely legitimate thing to do --- just, not here.

Usually we abstract that out to look something like

    myLayout = tall ||| Mirror tall ||| simpleTabbed

      where

        tall = Tall 1 (1/2) (3/100)

but if you prefer to do it inline then you'll want

    myLayout = Tall 1 (1/2) (3/100) ||| Mirror (Tall 1 (1/2) (3/100)) ||| simpleTabbed