Currently, swimlanes are auto-created every time a new combination of role/responsibility or system is entered into the "assign role" section of an activity.
This creates multiple swimlanes if the same role uses different systems within a process, resulting in a messy process map.
Having system tags in an activity is a useful function, though.
It would be excellent to be able to "switch off" the inclusion of systems as determinants of additional swimlanes.