This app was mentioned in 8 comments, with an average of 1.50 upvotes
Yes. I use this:
https://play.google.com/store/apps/details?id=com.genie.dimmer
it's nice cause you can set it to turn on/off on a schedule, it will dim the notification shade, you can set it to turn the screen brightness to the minimum when you turn it on, and it's got a quick tile. when you do turn it on there's a notification for it where you can increase/decrease the opacity.
Go to the display setting and add the app to the full screen apps list?
E: Or just open the app, hit the recents button and then click the full screen round button on the app window. Just tried it, it works except it seems to darken the nav bar you need pro.
E2: Or try this app, dims the whole screen. https://play.google.com/store/apps/details?id=com.genie.dimmer
That has been the go-to dimming app, but I just noticed it hasn't been updated since 2013. I was prompted to do a new check for dimming apps and found this better app. It's notification is much more useful letting you adjust the dimness without disabling it and dropping you into a bright interface, as well as letting you disable it from the notification, it's actually up to date (last updated 23FEB16), it actually dims the on-screen nav bar without root, and it's only 22kb in size!!
Also, Pixel Filter is useful for disabling a percentage of pixels on AMOLED displays, possibly resulting in improved battery life while dimming, instead of just applying a gray filter over everything.
Just use this: https://play.google.com/store/apps/details?id=com.genie.dimmer
I've been using it since OneUI 2.0, before extra dim existed.
I use Dimmer to fix it.