left and right side integration

[Xenovic]

It would be really nice if this could be used to place navbar items to
both the left and right side of the Gmail inbox.

You can insert a "lab addon" that puts your chat stuff on the right
side of the inbox, but there is a lot of real estate that is then
under that bar. Allowing for nav features to be on both sides of the
inbox would give more "above-the-fold" real estate...