I will say, we don't know for certain, but early reports from a claimed operations CM is that returning to the line will be through the
Lightning Lane, so you wouldn't necessarily draw attention to yourself when doing so. You would meet the rest of your party at the merge point where standby and lightning lane lines converge.
I can't really speak for exiting the line, as every line is different and finding a CM can be difficult.
In an earlier version of queue re-entry (called "bathroom pass") it was stated that you would receive a lanyard to identify that you were given a bathroom pass and could return to meet your party.
Currently the video chat CMs are recommending you talk to a CM before to join the standby line to ask about options. So if for example, you were given this lanyard (or some kind of pass) for return to queue when you joined the line, then you wouldn't need to find a CM before you exited and depending on the line, you might be able to exit quickly by opening some of the ropes. If you did not end up needing it, you could hand it to a CM before to boarded the ride.
At the end of the day, the recommendation to speak to a CM before you join the standby line is probably the best one and let them help you make a determination what option will work best for your situation.
As more people experience the various "new" accommodations available, I am sure we will get a better idea of how things work and you can decide what would work best for your situation.
Certainly, it would have helped if Disney would have communicated all of the options available and in a more defined way than they currently have. Most of the accommodations are listed on their website, but how they work in practice is not well documented imho.