Right click on the field you want to slide,
there is an option in the displayed menu "Set Sliding/Printing"
Select this and you can slide up the unused portion of the field
This will change how things appear in preview mode or when you Print/save as PDF. In browse mode, there will be no change.
When you select sliding, also select "resize enclosing part" and also set any objects, even graphic objects next to or below it such as a horizontal line, to also slide up/resize.