My thinking is that a single tab should be able to serve as the root tab for any given domain. (Not necessary to limit the functionality by domain, but it serves the example well)
eg, instead of having 12 github tabs open, I would be able to nest all 12 tabs beneath a single github tab.
I've searched pretty extensively and the only thing I've come across that supports functionality similar to this is an old chrome extension not available in the store anymore called IE tab multi
https://i.stack.imgur.com/1m6pw.png
Example of chrome extension running multiple tabs within a single chrome tab.
(sorry, not enough rep for images)
I think the multi tab addition was just a side effect of hosting IE within chrome though. I'm still going through the docs, just wanted to pose the question to see if anyone knew offhand.