your help was fundamental as always. I'm still waiting for a link of the video. I wonder why you didn't just point it out from the start.
As I've said, I already posted a video, showing the customizing works.
I think the issue with stairs not raising correctly is elsewhere, not related to the customization feature, but to the way the ground elevation is applied to the doors after they have been edited. That will be obviously looked at, I'm working on some new planes configs starting from scratch, to understand this.