Part of the problem is that I'm on my non-primary machine so I don't know which ones I'm missing

findbar.highlightall is essential for me

extensions.pocket.enabled

hide "are you sure" dialog when opening about:config

browser.urlbar.clickselectsall (now defunct)

extensions.checkCompatibility & friends (not sure if still necessary since I can't recall why I'm using it in the first place)

browser.backspace_action (might be platform dependent?)

browser.tabs.tabMinWidth

browser.compactmode.show

user.js customization because when I use tree style tabs there's redundant UI elements