If you layout controls with a GridPane is is suitable for many simple forms with rows of labels and fields, there are cases when you may want to conditionally hide some fields. When this is done, the GridPane still behaves as if there is a row with height = 0 and renders an inter-row gap on each side of this zero-height row. The result is not what you would expect when hiding fields on a form.

I suggest a tweak to add a property to GridPane that allows it to collapse adjacent gaps to a single gap in these cases.