In short, no. The existing ductwork and filtration system presumably have been sized for the current welding needs. To add a port and a new source of fumes would unbalance the system and compromise its integrity.
For example, adding a new port would cut airflow through all of the existing ports; this could affect capture rates. To add a new weld station to a system, an air quality engineer would have to run new calculations for the system and determine the power needed for the new arrangement.
Before adding a new collection point to your existing centralized source capture system, consult with an air quality system designer.