From https://support.mozilla.org/en-US/questions/1443060 Go to '''about:config''' in a new tab, type in '''widget.non-native-theme.scrollbar.style''', double click on the bar and set the value to 4, and click on the checkmark to confirm the change. Now go to a website with scrollbars and the scrollbars should be wider. <i>'''WARNING from the moderator team:''' Changing Firefox preferences from the about:config page can sometimes break Firefox or cause strange behavior. You should only do this if you know what you're doing. Please read [[Firefox advanced customization and configuration options]] to learn more. </i> I am not sure how much this will help, but for the hardware aspect, you can scroll with an ergonomic mouse or touchpad, both of which do not require using the scrollbar. https://nras.org.uk/resource/rheumatoid-arthritis-computing/ provides a few examples of things that can assist using a computer.