Do you have links to the userchrome tweaks that you use? I hear that mentioned a lot as a way to make sideberry better. IMO, the default for sideberry isn’t good. The few tweaks that weren’t outdated made things a bit better, but nothing really hit the mark. Like I said above, very willing to give suggestions a try.

edit: my main worry with relying on userchrome tweaks is things falling out-of-date or abandoned. I saw this a lot in my testing.

I only hide the main tab bar and sidebar header, both tweaks are copied verbatim from [0] (which is linked from the sidebery github readme) and the size of the window buttons block is corrected manually in a var.

Yes, tweaks going out of date was also my concern, but they're already a few years old and nothing broke so far. I reckon I could just adapt them if anything breaks, they're easy.

[0] https://mrotherguy.github.io/firefox-csshacks/

FWIW I do the same. It's the first thing I do on new installs of F'fox or Waterfox:

1. Open my email, download my `userchrome.css` file

2. Go to Help | More troubleshooting info | Open my profile folder

3. Make a folder called "chrome" in it.

4. Open my downloads folder.

5. Move the .css file from "Downloads" to "chrome".

6. In F'fox: go to `about.config` and enable legacy stylesheets.