One of my many FF / FF-Dev Add-Ons is
Tabby - Window and Tab Manager 1.1.6 true email@example.com.
I don't need to use it all the time, given mostly i rely on [& love]
tree style tab. However, when i sometimes load one of my bookmarks into the sidebar, i necessarily lose access to TST, & it's at these times that Tabby is useful for me.
Tabby is quite simplistic in the sense that it provides no direct graphical way for users to adjust its UI. It uses a huuuuuge font size, & i'm interested to learn if any of you cunning coding-competent Manjaroos know a way that a dweeb like me can reduce its font size.
I expect that it is likely
~/.firstname.lastname@example.org needs editing [is that even possible?]. Opening it in Kate gives gibberish, whilst Gedit refuses altogether to open it.