The next release (Q3 2012) is planned around the middle of October. We are looking into our VS designers, but at the current state of affairs I cannot provide an estimate on this.
For the time being, I can recommend using the source mode of Visual studio to add the markup by manually. Detailed information about the configuration of the different RadControls, is available in our online documentation:
You can also use the Properties popup of VS to configure the RadFileExplorer by pressing F4 when your cursor is in the its tag.
the Telerik team
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