Constraint rules should allow constraining blank numbers in the action section like they used to
Support confirmed that although this was supported in previous versions, and rules created in those versions still work, there is no way to do this or to edit one of those existing rules. The only work around is to make separate constraint rules for each blank attribute you want to constrain. A model will be kept much cleaner and easier to use if you can constrain all the blank values you need to constrain in one rule.
One suggestion was to use the "required" feature of an attribute. In every one of our configurations, we have found this to be inadequate or inferior to constraint rules for blank numbers. Here are some of the reasons...