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.

Thanks for the suggestion! Having a "per website" option would be a good idea. Perhaps I will look into adding that feature in the future.

Sorry to hear you are having issues with the add-on. If you email me at addons@wesleybranton.com, I'd be happy to help you get it working on your computer.

Thanks for the feedback! I'm always looking for ways to improve the add-on, so if you could email me at addons@wesleybranton.com with more information of the feature that you are looking for, I'd be happy to see what I can do.