Hi Sean,
The cable in the lower left port is a USB to RS232 Serial Adapter - used to provide GPS data to your transponder in order to generate ADSB-Out. This port (USB Port 2) is the most practical for allowing the cable to exit the end cover of Rosetta and will have been specifically configured in the PAW Configure Screen to provide the GPS data at the correct Baud Rate to match the Transponder, so it has to stay in that port. In practical terms therefore, your alternatives are limited to: -
1). The cheapest option - put the GPS dongle outside the case on a short USB male to female extension cable (but keep it the right way up - i.e. with the ceramic antenna uppermost), or...
2). Replace the existing GPS with a GPS Mouse (which has a standard width plug) which will then allow the new WiFi module to fit into the top-right port.
Sorry, a bit of a compromise, but the only practical options to retain ADSB-Out from your Transponder via GPS feed from your Rosetta and add iGRID.
Best Regards
Peter