When trying to create a blueprint Rule of 'Security Update' type, a lookup attribute that is expected to appear under 'Target Resource Attribute' dropdown is not there (it is based on a lookup that has the same NSQL definition as another out of the box lookup/attribute).
The original lookup is based in the Resource object, but the new lookup is not.
Set the object of the lookup to 'Resource': Classic Administration > Data Administration > Lookups > [your lookup] > General > Source > Dynamic Query > Object: 'Resource'.