"defer parsing javascript" in WP Super Cache?

No, you need to rearrange the way your Javascript is loaded.

Maybe a plugin that moves your JS to the footer can help https://www.ads-software.com/plugins/scripts-to-footerphp/

I tried it, but it slowed down my site for some reason. Seems that the human experience is better without deferring, even though Pagespeed is complaining, so i will ignore the Pagespeed result in this case.