[hank_z]

Can I ask how you use Sidebery and Tree Style Tab? I found that they both create a panel on the left side of screen and will stay there forever, which reduces the space for web content. The left panel also makes my small laptop screen look even smaller.

[ayushnix]

Sidebery and Tree Style Tabs make sense when used on a display with decent screen real estate when the viewport width is significantly higher than viewport height. I usually have more than 250 tabs open at a time which would be impossible to navigate without these vertical tree tab extensions.

[PetitPrince]

It's supposed to replace the tab bar. Unfortunately there's no API to do that and you have to rely on a custom userChrome.css.

Re loss of screen space: yes. However the reasoning is that losing some horizontal space is not as bad as loosing vertical space.

[littlecranky67]

To be fair, modern web design often maxes out at 1920p of screen width, often even narrower. You just lose whitespace.

[chrismorgan]

Though it depends on how you use your screen: if you like to tile windows horizontally, it takes more of your space. Tree Style Tab has a keyboard shortcut, F1 by default, to toggle its sidebar panel, and when I’m tiling side-by-side I often use it to close the tab bar for the moment. I’ve been surprised just how many pages are at least a little broken at 618px wide (what I get for two windows side-by-side, with the sidebar open)—I expected it to be rare, but while it’s not the norm, it’s hardly rare.

[moogly]

You can toggle the pane with F1.