Have a question about how the TVTropes wiki works? No one knows this community better than the people in it, so ask away! Ask the Tropers is the page you come to when you have a question burning in your brain and the support pages didn't help.
It's not for everything, though. For a list of all the resources for your questions, click here. You can also go to this Directory thread
for ongoing cleanup projects.
Can't speak for The Next Step (I don't watch that show), but as for Hetty Feather, I'd argue against the Christmas episode being treated as a Non-Serial Movie, as it features Sheila returning to work at Calendar Hall and she's still there at the beginning of season 6.
I was going to add some Christmas Episode specials to Non-Serial Movie but am not quite sure whether to add them or not.
What I planned to add:
I added to that page about an example from The Next Step of a Christmas Episode that was treated as a special but of uncertain canonicity.
In general, when should a Christmas Episode be treated as a Non-Serial Movie if there's no Word of God on its canonicity but in general, there's things that make it seem like it's outside the series'timeline/out of continuity?