Like many, I am a heavy user of the field validation rules engine. That's one of the key selling features of Knack. Often times I have validation rules that conditionally require a value to be set if another field has a particular value. For example:
If Field_1 is blank AND Field_2 is TRUE then show message "Field_1 requires a value, when Field_2 is checked."
Typically, this is configured on Field_1. However, there are many times when you want to prevent either field from changing value without the other. In this case, both fields need to have the same validation rule configured. This is cumbersome, especially when there are dozens of fields on an object.
It would be a major improvement if a feature could be added where I could check a checkbox to "copy" the validation rule to all referenced fields in the validation rule. It doesn't matter to me if the validation rule is editable on the other field, or just says something like "Copied from Field_1", with a link to the validation rules to that other field.
Alternative keywords: two-way, bidirectional, bi-directional