This is really wierd... I made some custom subscreens and saved the quest. Here's the weird part: When I tried playing the quest, the subscreens were all gone! I opened it up in ZQuest again, and all of the subscreens, (and the custom sfx) were gone! Then, when I tried to make another custom subscreen, I opened it as "(new)" but it was the classic style subscreen. This happened more than once, by the way.
subscreen bug (119)
Thus why I'm scared to use the builds. (sticking to b16c)
I think this is one of the known issues that they are working on.
But dang, that totally sucks!!
meh, it's ok. I have a backup quest file like the devs said everyone should have. :P