I didn't make any editions at Userchrome.css and I didn't find any way to export the settings I made, but I will keep looking to do the same with Firefox, for now you can replicate these settings through this step by step on Floor Browser.
- Design `about:preferences#design` -> Tab Bar Style -> Horizontal Tab Bar
- Design `about:preferences#design` -> Tab Bar Style -> Collapse Tree Style Tab
- Design `about:preferences#design` -> Tab Bar -> Optimise browser for Vertical Tab Bar
- Design `about:preferences#design` -> Bookmarks Toolbar -> Hide the Bookmarks Toolbar unless hovering over the navigation bar (Optional, you can simply choose to hide the favorite bar always)
- Design `about:preferences#design` -> Other Preferences -> Round the corners of pages
- Navigate to Sidebery Settings ⚙️:
- Sidebery Settings -> Help -> Import addon data -> Import the settings I left in Github
#### Step 3 (Last Step) - Customize Themes 🎨:
- Go to [Firefox Color](https://color.firefox.com/?fromAddon=true) (extension needed) and color according to your preferences or install [Darker Leo's](https://addons.mozilla.org/addon/darker-leo-s/) theme.
- Go to new tab (tabliss needs to be installed!) settings
- Background -> Upload Images -> Upload the image of your choice (I used this [site](https://www.sightunseen.com/2018/08/spanish-artist-ana-montiel-color-field-paintings-digital-art/), this [image](https://www.sightunseen.com/wordpress/wp-content/uploads/2018/08/Fields26-AllRealitiesCoExistingEverywhereForever.jpg))
- Widgets -> Remove all widgets and add Literature Clock
- Go to Customize Toolbar (By clicking on an empty place of the Firefox title bar)
- Add 5 Flexible Space to the left and right of the search bar.
#### Bonus: Other things
- If you want to use SplitView along with Sidebery, just add as a shortcut:
