I don't know if it works or not because whenever this extension is enabled, the player's settings button (cog shaped, top-right) stops working. The url changes still (#bottomsheet), but they never come up, so I can't check the video quality to tell whether it's ACTUALLY doing anything (other than that) or not.

It should be said though, I tried this because I hate how tedious it gets changing the video quality every single time I watch a new video. In the the settings for this extension, there is every option possible, from 144p, right up to H-est of HDs haha if it IS working, it's great! haha