I used to be a Tree Style Tab user, that is until I came across Sidebery which I found to be most useful. With Sidebery, I'm able to sort all my tabs and even configure the extension where specific new tab placement and I do not need a separate extension to enable the Unload feature either which I routinely do ensure memory doesn't fill up to fast.

The only thing I really do wish Sidebery is able to do is completely replace or even replicate Firefox's rather limited Vertical Tabs feature.