firefox-vertical-tabs VS FirefoxCSS-Store

I am trying to style the tab bar for Firefox to look like Edge browser's grouped vertical tabs. I am not very good at CSS and was trying to find a similar ready styling to use or easily edit, unfortunately, I couldn't. The closest thing was Vertical tabs for Firefox, inspired by Edge but it doesn't support tab grouping. Is there any other CSS I can try?

I use this CSS code with Tab Center Reborn to get vertical tabs. Unfortunately, the last FF update broke things (again). My close/minimize/maximize buttons are white and my back/forward buttons are gone. The author usually updates the CSS code quickly, but since I'm on an OLED display, I don't want a huge white rectangle on my screen.

Firefox have got this for long thanks to custom CSS.

Then I switched to Firefox with this: https://github.com/ranmaru22/firefox-vertical-tabs

Custom css: Thnx to u/0xMii for the custom css.

search for it on https://firefoxcss-store.github.io/ if you need assistance go to r/FirefoxCSS

yes, we can put "links of interest" on the web to collect all the communities, websites, or whatever related to firefox themes.

You can also remove that unnecessarily large sidebar header that Firefox insists on not letting users disable via normal means with userchrome mods. Some such setups can be seen at https://firefoxcss-store.github.io/.

firefox's ui is very customizable with css and i dont see why flatpak would change that. here are some examples https://firefoxcss-store.github.io/

I like to use this

If somehow this could be integrated with the css store down the line, I can see a lot more casual Firefox users finally trying out css customisations.

you can find others here https://firefoxcss-store.github.io/

You might want to take a look at Firefox CSS. There are some themes for home page and at the end of the site is guide: https://firefoxcss-store.github.io/