The Cartesian Chart Series for .NET MAUI visualizes ScatterSplineArea Series as the area enclosed by the coordinate axes and curved line segments that connect the series data points. The ScatterSplineArea Series inherit from the ScatterPointSeries class and also require both axes of the chart to be Numerical Axes.
The Numerical axis chart type is an indispensable part of the Cartesian coordinate system. The chart type calculates the coordinate of each data point on its actual numerical value this point provides for the axis.
See the .NET MAUI Charts documentation: Numerical axis
The Telerik UI for .NET MAUI Charts Legend feature displays a set of items, which correspond to the chart content making it easy for you to provide descriptions for the series visualized within the control.
You can use annotations in your Telerik UI for .NET MAUI Charts whenever you need to highlight certain areas or points on the plot. You can easily define annotations on any point of the plot area and customize their appearance.
See the .NET MAUI Charts documentation: Annotations