You get used to it and you don't.
It is not uncommon for me to use 3 different tunings over the course of a set. Sometimes it takes me a second to remember how I play that "G-chord" this time, but I always get there.
eventually.
I will say, I enjoy taking a song I'm used to doing in one tuning and moving to it another. Depending on how involved the song is it can be difficult, but two cool things happen. You learn more about the song and wrinkles are made in the brain that connect the two so it get's easier to transpose on the fly.
Ultimately, I think the goal is not to have to transpose at all, but rather just play the G chord. It's kind of like becoming fluent in another language. It's alot easier to speak it when you start to think that way too.