The stitch properties tab appears when a stitch design is selected. There are controls where you can add or remove up to 25% of the stitches by increasing or decreasing the density of the selected items. The slider controls will separately allow the adjustment of satin stitching and fill stitching, which allows very specific control.
If you are a DRK user, there are additional controls that also tie in to the Project Advisor and the Project system.