You can change the dpi of any app (including SystemUI) with xposed framework + "app settings" xposed module.
This will affect more than just the status bar though. Pie and navbar are part of systemui too.
Personally I always adjust the overall dpi in build prop then anything I want even lower, I use the module for
Which System App should I change? and any tips on what dpi you find working good when you mod the build prop?
And is it better do do it in build prop then just the system app?
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