@guilherm456 have you tried the web panel extension?
might be a solution for you. it's an excellent add-on, which allows you to open any webpage in your sidebar. it allows to bookmark pages as well.
All we want is side tabs and maximum vertical space. Why is it so hard for browsers to give us this simple obvious feature? First Chrome gave it and then took it away. Then Opera gave it and then took it away. Guess I'll try Firefox Quantum...
@leocg Apologies - I disabled my extensions and cleared my cache and the videos didn't autoplay - although it looked like the video was downloading in the background judging by the bandwidth used.
It seems the adblock plus extension is allowing the videos to autoplay. Unfortunately, adblock is pretty much the most essential extension to have an acceptable web browsing experience, so disabling it doesn't seem to be a good solution. I'll send them a message to see if they can help.