No Display Rule
Used to totally inactivate a Structural member from drawings. The No Display rule helps when you do not want part of your model processed into drawing views and you can't achieve it with forward view distance, or levels, or any other available technique.
The No Display rule causes subsequent rules that follow it in a sequence to select the elements that do not display. For this to work, it must always be set to "All" which is why the selection set options are greyed out.
Usage
One way the No Display rule this could be used is to create a seed dgnlib with all your standard rules and simply rearrange the list in each drawing as needed, including the No Display rule, items you don't want to see would be below the No Display rule in the list. An example might be that you have modeled all 'primary framing' and 'secondary framing' in one model and want to leave out 'secondary steel' like z girts or slab edge angles (if modeled to that level of detail) from a drawing."