No, for now, overlaying fields on top is still the only solution.
I've explored the possibility to extend wiki syntax with the ability to add buttons and input controls. However, the fact that there are various stencils that have different look for these controls, makes it even harder to implement this feature in a way that covers all use cases.
Perhaps a better solution would be the addition of a new Grid widget that acts as real container for other widgets, so that nesting input controls would be easier. We would have to let go of CSV and wiki syntax for this type of implementation.