I've spent hours on this same issue and searched your doc multiple times before finding this post. This should be in your product documentation, not "documented" in this forum post.
answered on 06 Feb 2020, 01:09 PM
All of the functionalities that are exposed by a certain widget are documented and placed in the API reference of the respective widget. Since the documentation aims for clarifying a whole concept a functionality rather than very specific ones, you could search in the API article of the Sparkline widget: