My personal userChrome/userContent, tailored for Materia Dark KDE theme or just dark UI in general (also works fine in Windows).
These are fully experimental and hosted here mainly as backups.
- Minimal mode. Only pinned tabs and active tab will be visible above URL bar (native Title Bar must be disabled). This is to be used with Tree Style Tab extension.
- Auto-hide sidebar when fullscreen (intended to auto-hide Tree Style Tab sidebar).
- Auto-hide sidebar when there's only 1 active tab (intended to auto-hide Tree Style Tab sidebar; unfortunately requires Tab Count in Window Title extension).
- Various tweaks to Tree Style Tab sidebar itself (TreeStyleTab.css)
- Dark theme in built-in home and new tab pages, GitHub raw files, local files, blank pages (matches Firefox's built-in dark color scheme).
- Find bar (Ctrl+F) moved to the top.
- Removed URL bar's background and borders.
- etc.
- Update dark color scheme for Reader mode (currently using an old color scheme based on Arc-Dark).
Open Tree Style Tab's preferences through Add-ons > Tree Style Tab > Preferences.
Enable Proton theme in Appearance > Theme.
Then use the content of CSS file in Advanced > Extra style rules for contents provided by Tree Style Tab.