Hi,
When you play outside, when the sun is full on and there is no shade, how do you shade the sc live 4 screen?
Beside using the foul brightness and settings
Please don’t do this. Playing in full sun can become a hardware risk in extreme conditions. Dark plastic surfaces absorb a lot of radiant heat, and without shade or airflow the casing temperature can rise much higher than expected.
Take good care of yourself and your Denon DJ SC Live 4. A foldable canopy, umbrella, or small pavilion makes a big difference … and they’re relatively inexpensive, even custom-branded with your logo if you want one. 
I bought these from ebay ages ago for my mixstream pro go, pack of 2 & I’m still using the the 1st one good quality flexible hardish matte plastic distorts sun reflection but you can still see the screen. You can get them for all devices so pick the right one.
https://www.ebay.co.uk/sch/i.html?_nkw=Denon+sc+live+4+screen+protector&_trksid=p4624852.m4084.l1313
As others have said … forget about keeping just the screen viewable …
There’s no point in the screen being visible if the entire system keeps shutting down due to heat / sun conditions beyond the machines operating tolerances
Similarly, There’s no point in the screen being visible if the DJ has passed out due to heatstroke
Get a parasol with a clip on bracket to connect to your folding DJ booth, speaker pole, your DJ table, a chair, anything - protect yourself and then worry about all of your gear, not just its visibility