Yes, the HMC/MLC can be configured as a Modbus TCP Master on COM3 and still retain the default Modbus TCP Slave configuration.

You must choose one or the other between master and slave for Modbus RTU, but Modbus TCP can be both simultaneously thanks to Ethernet. As a master (client) you can read Modbus data from, or write Modbus data to, other Modbus TCP devices.