The Idea :
In Preview Mode, when a part is resized because of sliding options of enclosed objects, there should be a way to resize accordingly some other objects.
When you are designing a printing List View Layout, the customer often will ask you to have columns delimited by lines. With FileMaker, this *so simple and common thing* always has been impossible when the body contain sliding objects that reduce the Body height.
In essence, when you put your vertical lines inside the body, even if these lines are checked "Sliding up…" and also "Resize enclosing part", the body will not resize because lines are sized to fit the actual (maximal) body height. But there should be a way to achieve *that*, isn't it ?
A new sliding option "Fit to enclosing part height" could be fine.
Example in attach if necessary.