I was excited to find that the update brought the ability to fit the doors in workshop mode into the pre-existing doorways. Not -all- doorways though.
I only tested the ones in Sanctuary. I got the doors to fit on the one in the video and the empty doorway on SS house, on the side where the carport is.
Maybe next update will let them fit ALL doorways.
https://www.youtube.com/watch?v=AbYXpT5Qc-M