Unable to add new folders on iPhone XS

As far as my knowledge goes it is 216 apps in a folder.

Please see a screen recording below where I have tested it for 27 apps. I would not like to test for 216 apps because I feel it is counter-productive when you already have the App Library.

After adding 20+ Apps or so Drag other apps to the Folder and hold it there above the folder for a while let the folder open and arrange the apps and it will create space for you additional apps.

See the pic below on the iOS Mail app.