The Good 'ol Sidebar (TGS) is a sidebar control, fork of All-in-One Sidebar .
The Good 'ol Sidebar vs All-in-One Sidebar opinions
CRITICAL TO ME, to open Bookmarks Library IN NEW WINDOW with single pane and telescoping folders.
It improves upon the current features of All-in-One Sidebar and fixes a few bugs that were left broken in AiOS.
This add-on for Firefox provides a few options to make the sidebar more accessible and customize it.Discontinued
The add-on will not receive any more updates and will stop working by next November with Firefox 57, when XUL-based add-ons will be deprecated in favor of the WebExtensions API. See http://fasezero.com/ The extension still works on XUL-based Firefox forks like Waterfox and Pale Moon
OmniSidebar vs All-in-One Sidebar opinions
OmniSideBar is open-source (which All-in-One is not), reliable and highly functional. It's also more regularly updated than is All-in-One Sidebar, but offers the same functionality. I've used it for 2 years+ and never looked back.
Slim vertical button to toggle Firefox's (57+) sidebar on/off, on the left of browser. Firefox has native sidebar but no native switch to be touched on the edge of browser. This userChrome script provides experience like All-in-One Sidebar.