Here are some examples if aiming for near 100% extension support. Tab stash https://addons.mozilla.org/en-US/firefox/addon/tab-stash/?utm_source=addons.mozilla.org&utm_medium=referral&utm_content=hotness Tree style tabs https://addons.mozilla.org/en-US/firefox/addon/tree-style-tab/?utm_source=addons.mozilla.org&utm_medium=referral&utm_content=search Todoist sidebar https://addons.mozilla.org/en-US/firefox/addon/todoist_sidebar/?utm_source=addons.mozilla.org&utm_medium=referral&utm_content=search Youtube sidebar https://addons.mozilla.org/en-US/firefox/addon/youtubetm-sidebar/?utm_source=addons.mozilla.org&utm_medium=referral&utm_content=search History sidebar https://addons.mozilla.org/en-US/firefox/addon/the-history-panel/?utm_source=addons.mozilla.org&utm_medium=referral&utm_content=search Currently there is a native sidebar, so the solution would be to load the sidebar extension whenever the button of the extension in the sidebar is clicked? It can be placed inside the "Library" folder in the sidebar.
When they are opened, they can simply look similar to this: Except the "Bookmarks" title is replaced, and the arrow is added.
The sidebar still seems to kinda work?
