Scrollbars size could be setupable from toolbar icon (popup window)

[fastaddons]

Let's say user has hidden scrollbars. If there is a problem on the page and he wants to see them now, he has to go to Options page and change it there.

It may be a good idea to put simple 3 value switch (maybe icons) to the toolbar icon popup where one could simply click to change scrollbars.

[InvisiBot]

I use a laptop with a small screen sizes and It helps me functionality is "the thin scroll bar" for the release of usable space.
But sometimes there are web pages that are placed on the small screen width only if you remove the full bar on the right scroll bar.
Therefore, a quick scroll bar mode switching would be very helpful for me.
In addition, it would be nice if the application will have the function of "memorizing scrollbars setting for this URL".

Sometimes I podlyuchayu laptop to the big screen and I would like to see a full-size scroll bar. Therefore, I find the idea of ​​a fast switching scrolbar very useful.

[InvisiBot]

Does Firefox opportunity to the user to choose the thickness of the scroll bar? I would play with the size of 2-3px.

[Juraj-Masiar]

Does Firefox opportunity to the user to choose the thickness of the scroll bar? I would play with the size of 2-3px.

Nope, Firefox supports only those 3 modes;
https://developer.mozilla.org/en-US/docs/Web/CSS/scrollbar-width