Field Validation can be used to make a field required based on certain conditions. Here's how:
Go to the field you want to be required in certain cases
Go to the Field Validation section
Add one condition group
Add two conditions to the condition group and make sure the logic inside the condition group is set to AND:
The first condition determines when the field has to be filled out
The second condition specifies that this field needs to not be empty in this case.
Together, these two conditions will ensure that the field needs to not be empty when the other field is set to a certain value.
Add a condition outside of the condition group, and set the logic to OR:
Add the opposite condition to the first condition inside the condition group, to ensure that the field is always valid when it doesn't have to be filled out.
Here's what that could look like in the configuration:
