Multiplexing into Windows

Usually most efficient into USB, but can also simulate multiple serial ports

Each NMEA 0183 device plugs into a serial port on the multiplexer.

Specific device testing/manufacturer specifications are required to know how to wire the NMEA 0183 device and whether to bring its serial electrical output as RS-232,  RS-423, or RS-422

Multiplexers vary in electrical interface and number of ports, such as
What if something breaks?

It may be possible to program computer applications to recognize a primary and secondary device.
If not...