I know Firefox has a Split View feature; however, it’s not as convenient as Vivaldi or the Arc browser. I love how The browser company implemented the Split View screen. Firefox Split View is pretty limited, and I’m unsure if it has improved since its release.
What does the community think about that?
Here is an example of Arc browser split view:
I have this addon. This is not Split View.
Even Floorp (Firefox fork) has a built-in split view, however it pretty limited. https://file.coffee/u/oEGzVEe8jr2N8Z6gtqL1F.gif
This is just the Firefox addon you have linked previously that is called "Side View". They just changed the limitation of the sideview panel. You can remove the restriction too, but need to edit files and create folder in your Firefox user folder. Obviously this is not something most people do, but I am used to it and edited a lot in the past.
Here is a screenshot where I drag the size of the Side View / Split View to half of window (it can take entire size, normal tab is on the left and side view on the right):
https://superuser.com/questions/1276800/customize-the-maximum-width-of-the-firefox-sidebar
That makes sense. I’m using Floorp, which already has many CSS tweaks built-in; however, it is pretty limited, as you saw in the gif. With Arc, you can have as many Split/side Views. It’s one of their main selling features.
I would have a look into it (just out of curiosity, I'm happy with Firefox), but it's proprietary and not open source.