Purpose
It's a validator for doing any of the following checks:
- A field is initialized.
- A field is not initialized.
- A field has been edited in transition screen.
- A field hasn't been edited in transition screen.
For cascading select fields both levels are required to be initialized.
Example: Check that field "My Date" hasn't been edited in transition screen
SINCE VERSION 2.5.0
Since JWT version 2.5.0 it is possible to choose that all values in a multi-valued field have to be checked: