Concerning your first question:
To prevent the trailing part of the tooltip which points to the textbox from being displayed, merely set the ShowCallout
property of the tooltip control to false.
Regarding your second question:
Does tweaking with the location-related properties of RadToolTip presented in this demo
or increasing the z-index value
of the control produces the desired result with the charts from the dashboard? If this does not help, please send us a screenshot or a sample project (representing the discrepancy) attached to a formal support ticket under the RadChart or RadToolTip category. Thus we will do our best to advice you further.
the Telerik team
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