Same problem on S8 Edge+. Since your post was in April and it's now June 20th, with no other replies to your post and no change in the problem, it's apparent that TeamViewer doesn't review these messages. That's sad to learn! Guess we'll need to submit the feedback another way...
Do you have a paid license? I used to just email their support, but they sent me an auto-reply saying they're only helping paid customers now. :(
I don't know why but this may work for you too.
Run Teamviewer Desktop app first and Start Host app from S8 then the navigation bar will be removed.
If host is already running you have to kill it first. (or just reboot)
I have problem with the navigation bar on my S8 plus. My problem is that the key at the right side of my navigation bar (Either back button or recents button) doesn't respond properly. Only the right side button is more unresponsive. Earlier I had problem with the recents button that it was too much responsive. It automatically responds without even touching it. The touch on that area is working normally when using other apps.
Can anyone tell how to issue the navigation bar on PC connected window for note 8 when device is screen off ?