This is awesome! But I think your Youtube link is to a Stylus tutorial, not Stylish. I’m a tech idiot and was able to get it running quick without any videos. Spoiler alert:
IT WORKS!
I made some screenshots from Firefox, but I’m not allowed to put them in a reply (is this because of my Guest status?) I’ll try to describe. Again, this is for Firefox:
First install the extension, then in the Add-ons Manager, click the three horizontal dots next to the Stylish on-off toggle.
Then click Options in the dropdown. A new browser tab opens up. In the left panel, click Write New Style. Then in the big box on the right side, paste in the code provided by AnalogSignal above. Give it a name and hit Save. I ignored some warnings about the code – they caused me no problems.
Finally, in the upper RH corner of your browser (usually – I guess), click on your new add-on button. Toggle on and off by clicking “Stylish On” or “Stylish Off”. You may need to refresh the page.
Worked like a charm. A real improvement – thanks, AnalogSignal!