LineSeries uses a categorical XAxis, while the ScatterSeries and ScatterLineSeries use a numerical XAxis. The RadHtmlChart does not let you mix a Series of different types. You can have a look at this
online demo related to mixing chart Series.
Regarding the callouts, RadHtmlChart does not support such functionality. You can, however, achieve that effect by creating and aligning styled div/span elements that contain the desired text over the desired area from the RadHtmlChart. There is a good example on the KendoUI's Bubble chart demo
, that show how to create a legend manually through such styled div element.
All the best,
the Telerik team
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