These properties rule the appearance of the container that contains the Widget within the Dashboard.
results in :
Show a border line around the Widget.
By default, Border Color is managed by the currently applied Theme.
However, you can override the Theme color for the Border Color by checking Override Border Color and selecting the desired color.
Define the thickness of the line defining the border color, in pixels.
Round the corners of the Widget container, to turn it into a rounded rectangle.
Header settings : see previous chapter about Header and Description.
Note : accessing Border options on other Widgets
Some Widget types are not edited through the Widget activity tab, and don’t have a “Container Appearance” section : Image, Label, Embed, …
For those Widgets, the Border options can be accessed in the top bar when the Widget is selected :