Forget Quality Score.
It’s such a dodgy metric that Google hide our historical Quality Scores from us.
Download your keyword data for a data a while ago, and look at the Quality Scores.
You will have all the other metrics from that date, but the Quality Score that you’ll see is your current one.
The only way to see how your Quality Score has changed over time is to download the keyword data every day and store it.
Seems a bit fishy to me.
I mean, they have the historical Quality Score along with all the other metrics, but they have ADDED a bit of extra programming to replace the old Quality Scores with the current Quality Scores when you download them.