Whops… The documentation is wrong here. At the moment we have intentionally disabled layouts in layouts to avoid complex scenarios for developers - and potential pitfalls for the users.
However, we have discussed supporting layouts in layouts for defined cases:,
I.e. if the developers creates a 1 column layout that simply adds nice padding or similar. It would indeed be interesting to place this layout inside other layouts? In that case the developer would have to declare that this layout can be placed inside other layouts? What do you think?