The Scripts were tested on Firefox 69 stable build.
Vertical Add-on Toolbar --- Single Column with scrolling, Multiple Columns
Status+Addon bottom toolbar --- Image
Auto hide tab bar only when Tree Style Tab sidebar is selected and visible --- Gif
Movable Page Title on Toolbar --- If you're still not sure what it does, check out these Gif, Gif
Duplicate tab with double-click --- Direct, Background
You can visit this link to learn about userChrome.js
There are several ways to do so, I can't say this is the best way to do so, but it's the easiest method. My scripts were all tested under that method by the way.
Also, if you are unfamiliar with userChrome.css (userChrome.css and userChrome.js are different), you should take a look at these links: info, how to.
For Firefox 72+, checkout this repo to add userChrome.js support to Firefox.