Hi Guido,
Only a single tooltip might be visible at any given time. This behavior is by design and will not be changed as changing it would defy the purpose of the control.
The purpose of a tooltip is to provide additional information for a given element. It is not meant to be used as a popup control or as a draggable panel. That is why method as hide_all is not applicable for RadToolTip and thus there is no such implemented.
Regards,
Svetlina
the Telerik team
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