I have just noticed, on a fresh install of Windows 10 on my tablet, that the Mail and Calendar (and probably more, the list is a lot shorter than on my main PC) are not in the list. Has anyone else had this problem?
you mean Notifications on settings? well the notifications only get added when an app displays a toast notification. that's the only way. This is a problem too because some desktop software use toast notifications and you can't remove them from the list even if you uninstall the program or it was a random installer displaying it.
But if you have used apps but they never displayed a toast notification, then the app will not be on the list.