Depends.
In general the various Canons were set in stone around 200-400AD and have remained stable since then. There was the minor change in the Protestant Canon at the Reformation, but that is one of the few examples.
BUT...
various sects have accepted new books. The Mormons are a good example. Down through history other groups at times accepted other books as Canon, particularly the Gnostic Gospels.
The point is that as much as they would like to claim inerrancy and infallibility, there has NEVER been one universal Canon, and it is unlikely that there ever will be such a critter.
The best they can do is shout "Mine, Mine, Mine" and stick their fingers in their ears to drown out the voices from all the others that have the
Absolute Truth® who, like them are shouting "Mine, Mine, Mine".
Aslan is not a Tame Lion