In shot no, you cannot 'extend' the are of the splitbar where you can click and drag it in order to resize the panes.
The functionality of the splitbar to resize the panes using the mouse is implemented using various event handlers attached to the <html> element of the splitbar, so to utilize the resize functionality you need to click inside this element. When the RadSplitter's SplitBarsSize property is set to 1 the splitbar's element is rendered with 1px width, thus clicking on the splitbar is indeed hard.
With the current rendering of RadSplitBar the required functionality cannot be achieved and we do not have modifications in this aspect for the near future.
the Telerik team
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