Cross field validation would be a helpful feature in many use cases.

Here three examples:
1. If you enter a value for an asset field, you also must provide a value for the asset description field that is present in the dialog.
2. In the Composite field "Point of interest", you must always fill in a longitude and a latitude, or leave both empty.
3. Two fields, age & parents names: If age < 18 one must enter a parents name.

This would be a very helpful feature to make the usage of forms more flexible.

I have created an issue where I tried a cross field validation on a CompositeField (constrained scope) as a POC, the POC would be usable: MGNLUI-3241