The Stroke Visibility option is an On/Off toggle used to set the visibility of strokes/lines of a figure(s). If the visibility option is turned off, the border/line of a selected or added figure(s) is not drawn at all.
The Stroke Visibility toggle is accessed by clicking on the Stroke Tab in the Sidebar, as shown below:
Click on the check box next to the Stroke label to enable or disable the Stroke Visibility option.
If Stroke Visibility is on, an outline around the figure will be present, and if it is off and Fill Visibility is on, the figure will appear with no border, as shown below:
Note: Stroke attribute changes will not be reflected in a selected or added figure(s) until this option has been enabled.