It doesn't work with Synology interface about custom-scrollbar HOT 1 CLOSED

Firstly, glad to hear that you find the add-on useful. I think accessibility is something that a lot of website developers forget about when designing their website.

As for your issue, this type of thing usually happens for one of two reasons: A) Firefox does not allow add-ons to modify some pages. This most notably includes many of the Firefox-owned websites and internal Firefox pages, but this also includes the pages created by other add-ons or some pages that are shown by software installed on your computer (eg. a router settings page). B) The website is preventing scrollbar customization. Sometimes the website has created custom elements that are technically scrollbars but behave like ones. That allows them full control over the appearance and behaviour. There are other ways that websites can also prevent customization.

Unfortunately, in my experience, these scenarios are very difficult for the add-on to prevent.

I'm not sure exactly which Synology product you are having an issue with, but since Synology is a proprietary product that requires payment, I probably won't be able to dig any deeper into this.

from custom-scrollbar.