It can mean the difference between a single $170 filing fee for one case or $340 or more for multiple cases. Some judges will let litigants do this and save a filing fee, but Court Operating Rule 4.05.3 controls.
Dissolutions and paternity actions shall be filed separately. A separate case number shall be assigned for each dissolution and each paternity action filed and shall be related in the automated case management system for scheduling and other processing.
— COR 4.05.3