How to make side panel resizable:
Updated instructions for Feb 2024 (I'm on Firefox version 123)

- Go to about:support
- in Application Basics section find row called Profile Directory, click on Open Directory button
- Close all firefox running instances
- In that folder, find xulstore.json and open it with a text editor
- Find where it says "sidebar-box":{
- inside those brackets look for "style":
- inside this find width: and replace with the following:
width: 50%; max-width: none !important; min-width: 0px !important;

- if you did it correctly it should look like this: "style":"-moz-box-ordinal-group: 3; order: 1; width: 50%; max-width: none !important; min-width: 0px !important;","checked":"true"

- save the file and close, open Firefox and have fun :)

I hope to see Side View fully implemented natively in Firefox soon.

But it isn't useful as is, with the limited width. I had to fix this with this guide:
https://superuser.com/questions/1276800/customize-the-maximum-width-of-the-firefox-sidebar

Required a change in about:config for me:
(toolkit.legacyUserProfileCustomizations.stylesheets = true)

this what im looking for ! its link split screen in microsoft edge i love this extention!

Can someone maintain this plugin?
Some important features are missing:
* Ability to add multiple website icons in link or right panel.
* Click on any icon to open its website in the panel.

They are useful for workflow!

They would be like Vivaldi side panel

If I had known about this feature, I would never have left Firefox for Edge. (Please add this as a built-in feature.)

Edge had another very productive feature called Web Select, which allowed users to copy text with formats. It was based on their built-in web capturing feature, but unfortunately, they deprecated it. Now users are upset, and Bing Chat is not a very useful feature to keep people with Edge.

Please add a Web Select-like feature to Firefox Capture. This is the last thing I need from Firefox. Great work! You are the pioneer of browsers. Thanks!

Option to choose and follow the color theme of FIrefox would be welcome,

Very good extension by the way !

Hope this gets continuous support.

Firstly, big thanks to the creator for this addon.

Secondly, I have to admit I don't use it in the intended way but rather as a workaround on sites attempting to block adblockers. Specifically Twitch. I don't know how it seems to work, but Twitch will block me from watching streams with an adblocker by giving me an error 90% of the time.

I started using this to circumvent it. For some reason, opening the stream in this side tab will FORCE streams to load in the main tab 100% of the time. Thank you, because without this I'd not be able to watch twitch with adblockers.

Для увеличения боковой панели
1. откройте about: config в Firefox и установите для параметра toolkit.legacyUserProfileCustomizations.stylesheets значение true
2. Меню Firefox -> Справка -> Информация для решения проблем -> Папка профиля -> Открыть папку, создаём папку Chrome
3. В папке Chrome создаём текстовый документ и вставляем в него текст
#sidebar-box {
max-width: none !important;
min-width: 0px !important;
}
Сохраняем и переименовываем в userChrome.css
4. Перезагружаем браузер и радуемся неограниченной регулировкой размера боковой панели.

I Love what this does. It is actually a very simple concept - but keeping your calendar or a cloud or mail acc handy on your sidebar shortens my workflows extremely.
I wish they would continue working on it, since I have seen that the last update was in 2018 :/