Making fullscreen windows not tiled in xmonad + KDE

"You can't plug it in directly because the types don't match:

ghci> :t isFullscreen -?> doFullFloat
isFullscreen -?> doFullFloat :: MaybeManageHook
ghci> :t composeAll
composeAll :: [ManageHook] -> ManageHook

Note, however

ghci> :t composeOne
composeOne :: [MaybeManageHook] -> ManageHook

That takes a list of manage hooks that may or may not run and combines them into one action.

MaybeManageHook also fits nicely with

*Main> :t maybeToDefinite
maybeToDefinite :: MaybeManageHook -> ManageHook

Add either

, [ maybeToDefinite (isFullscreen -?> doFullFloat) ]

or

, [ composeOne [ isFullscreen -?> doFullFloat ] ]

to the definition of myManageHook."