"You need at least 6 tiles"

[Renate]

No, I don't.

The pull-down "Control Center" has "Quick Tiles" that you can edit.
But it will squawk if you desire less than six.

To fix this you don't even have to be rooted, but you need ADB.

C:\>adb shell
$ settings put secure sysui_qs_tiles eink

This will leave you with just the "Eink Control Center" as your only tile.
But don't worry. You can drag the other tiles that you would like in also.