You want your Windows 10 Taskbar (the one with the Start menu button) to hide when you are not using it?
Or you want your Firefox toolbars to hide (roll up) when not using them? In Firefox, you would use full screen mode -- you can use the F11 function key to switch into and out of browser full screen mode.
More info: Use Firefox in Full Screen mode
For Windows, you may need to check Microsoft's help if the feature is not working as expected. I see there are a lot of questions on their forum: "windows 10" taskbar auto-hide site:microsoft.com - Google Search
You want your Windows 10 Taskbar (the one with the Start menu button) to hide when you are not using it?
Or you want your Firefox toolbars to hide (roll up) when not using them? In Firefox, you would use full screen mode -- you can use the F11 function key to switch into and out of browser full screen mode.
''More info:'' [[How to make Firefox and websites go full screen]]
For Windows, you may need to check Microsoft's help if the feature is not working as expected. I see there are a lot of questions on their forum: [https://www.google.com/search?q=%22windows+10%22+taskbar+auto-hide+site:microsoft.com&client=firefox-b-1-d&source=lnt&tbs=qdr:y "windows 10" taskbar auto-hide site:microsoft.com - Google Search]