If it were only that simple [:((]

You and Emmanuel have wright.
I've tried to find a general formula but I've fail (until now).
A possibly workaround could be to have a specific prefix for fixed part (only one) on every adjustable model prefixed with sweethome3d_fixed_[part-name] like sweethome3d_fixed_exterior-frame
which could be used as references for YXZ.
I could also to add another custom property to roof windows and, to plugin, a deformation listener but this will produce a significant slowing of the entire program.
So, at that moment, I will let it as is.
With/Without this I'm wait the final 7.2 release to enjoy discovering the news [:x]