This is a great add-on!
I always have too many tabs opened and recently Firefox (85.0.2 64-bit) ate up more than 60% of my CPU-performance and 90% of the (16GB) RAM. After I have installed this add-on and have used "unload other tabs", Firefox only needs about 3% of my CPU-performance and 25% of the machine's RAM any more.
Thank you very much for your time and effort programming this add-on! I hope that there will be updates for this add-on in the future if necessary.