Glad to hear that you like the add-on.

Unfortunately, the size option is limited to what Firefox options are currently in Firefox. At the moment, they just offer the two, but I'm hoping they will eventually add more custom settings.

As for the site-specific settings, that's on my to-do list.

Glad to hear you like the extension!

Currently, it's not possible to add a fully custom width. Firefox only provides regular, thin or none. Hopefully custom widths are something that Firefox will support in the future.

Glad to hear that you like the add-on!

I'd love to be able to do this. However, it's not currently possible due to the approach that Firefox takes when it comes to customizing the scrollbars. I really hope it will become possible in the future though because I think it would be really cool to give users like yourself more control over the appearance of the browser.

PS I left you a more detailed explanation on the request you posted on the GitHub repository: https://github.com/WesleyBranton/Custom-Scrollbar/issues/14

Currently, having a "hide when not in use" option would be near impossible to do without severely impacting performance. If something changes in a future version of Firefox that makes this option more doable, I'd love to add it, since you aren't the first person to have suggested this.

As for the issue that you are having, when I test on my computer, nothing about the drop-down menu on pages change for me. This isn't unexpected, since the drop-down selection elements on pages are treated as part of the Firefox UI, which cannot currently be modified by add-ons.

However, if you are getting some other behaviour or something is breaking on the page, please feel free to email me at addons@wesleybranton.com with a link to the page you are having issues with, the settings that you are using, what operating system you are using on your computer (Windows, Mac, etc) and a screenshot of the issue.