It's easiest via the Config program. Just right click on a source, change the name in the dialogue box and store the configuration to your G95. It's probably possible via the front panel but it's not a route I've tried personally

Main system - Sources (Kodi-HTPC, Vero 4k, FireTV, Sat) into Trinnov Altitude 32 (8-16) (+Roon), Trinnov Amplitude 8 amp & Vivid Audio (Giya G3, V1.5) and REL Stentor III speakers. Others: F80 + Raspberry Pi and other Pi systems.