I have given up. Tabs Outliner is abandoned.
Now I use BrainTool. It's closer to bookmark manager than TO, but that is actually a good thing. With TO it was very easy to lose your tabs (e.g. you open a folder full of tabs and close the tabs from Chrome and boom they're gone). Braintool doesn't try to take care tabbing that much, though it has Tab Grouping for example. What I really like is the clean hierarchical structure, with voluntary notes attached to each bookmark. And it makes a simple org-mode file that's accessible via text editor or online editor (https://organice.200ok.ch/). Developer is nice and actively developing the plugin, check it out.
On chrome extension page is says that Tabs Outliner is on version 1.4.137 and was last updated 30.04.2020?
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