I have a GMRS radio and VHF/UHF radio in car. I have an antenna mount and cable installed. I install appropriate antenna for the radio in use and manually remove and attach cable to matching radio. It’s a PITA. Is there a way to split the cable to go to both radios? So I don’t have to remove connections. I saw an A/B switch. But was hoping I could use a T connector or something. See illustration.
You need a switch. Connecting two transceivers directly to one antenna is a great way to destroy one of them — as soon as you transmit with one, the receive circuit of the other one will see several million times more power than it's designed to handle.
If you only wanted to use 2m on the ham rig then you could probably use a diplexer to send the 2m frequencies to the ham rig and the GMRS frequencies to the GMRS rig, and get enough isolation between them to avoid trouble. But the 70cm ham band and the GMRS band are too close together to make that idea practical.