The custom style properties accessor of a VisualElement (Read Only).
To get the custom styles properties of an element, call the ICustomStyle.TryGetValue
method to query the returned object of this property.
For more information about how to use this property, refer to the
Get custom styles manual page.
For a list of all the supported style properties, refer
to the USS properties reference manual page.
Additional resources: VisualElement.style, VisualElement.resolvedStyle