This app was mentioned in 4 comments, with an average of 2.75 upvotes
For me, Xposed and MIUI Tweaks made MIUI feel almost like a proper 'custom' rom and not something you'd find in a Samsung or an iPhone.
No need for gravitybox. There's two different xposed modules that spceifically tweak MIUI, you can find this feature there.
https://play.google.com/store/apps/details?id=com.hartec.miuitweaks8&hl=en
https://play.google.com/store/apps/details?id=software.solarwarez.xmiui&hl=en
And you're done.