Lower the minimum brightness without third party apps

My default lowest brightness value is around 33. I can't go lower than that from the brightness slider. 33 is too bright for me. I want to take it even lower near 15. Although I can lower it to 15 by modifying the brightness file located in sys/class/backlight/ it is temporary. So I want an permanent solution like changing some values here and there. I don't want to use an third party app as they're inconvenient and create issues oftentimes. I'm using Pocophone with a custom ROM Android 11. And I have Root access with Magisk 24. So I can do pretty much anything.