Usage:

Drag and drop tabs to reorder them and create trees.
Click on the favicon of a tab to expand/collapse his tree.
The arrow to the right of a tab means that the tab is a collapsed tree.
Press "F1" to display/hide the sidebar.

How to hide the Firefox tab bar and the sidebar header: Add this code in your userChrome.css : #TabsToolbar, #sidebar-header { display: none; } How to move the "new tab" button to the url toolbar: Right click on the "new tab" button in the Firefox tab bar , select "Customize" and drag and drop the button in the url toolbar