In regards to making/editing maps, today I learned that this entire time I didn't have to give door linedefs a tag if the sector acting as the door uses said linedefs. Specifically "switch" doors (SR/S1 functions).
Before this accidental discovery, I would assign the "door" sector (and the two "switch" linedefs that sandwich the sector) a tag but as it turns out, this is unnecessary in this case. I thought all functions (except for texture scrolling) NEEDED a tag in order to function. I'm still a bit of a newbie but I'm getting better!