Enhance Vertical Tabs by letting Tabs spawn sub-tabs instead of having them all be equal

[Loot]

I like the new sidebar, it would save me a browser extension if it would be tweaked just a little.

If you look at the extension "tree style tabs" they do it a little better or more convenient at least.

When I open a new sub-Tab from an existing Tab the new one will be below and slightly to the right 

So you can see that it is under the "master-tab" and you can minimize all sub-Tabs by clicking

a little arrow on the master-Tab.

[Jon]

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