I ended up ditching Chrome and switched to Firefox, because currently all the available Chrome tree-style tab managers are sucky. on Firefox I'm using Tree Style Tabs and it's basically a much better experience as you can configure it using CSS. Even if you don't know CSS like me, there are snippets and all you have to change is a number and coerce it to look how you want by trial and error.

I had high hopes that Tabs Outliner for Chrome would continue to evolve and improve, but that has not been the case for a long time so I had to look for an alternative. Overall, after tweaking Firefox to my liking, I'm actually finding it to be much more powerful than Chrome. A couple of things work better in Chrome but I can easily live without those. Being able to manage large numbers of tabs efficiently really saves a lot of time, and Tree Style Tabs is 100% free so you get the "full experience" and no ads or BS.

Hi Vlad, hope you are well! Just curious, are you still developing TO? It's the most useful Chrome extension I have used. I was considering to buy it but multiple item selection is really needed. Thanks

Any news on this one? I modified the file black-Linen.png using MS Paint, but Tabs Outliner crashes. I don't understand why.

That pesky flag!! I thought I was going crazy. This thread solved my problem of tabs not being removed from the list.