The Kendo UI Editor expands and shrinks horizontally automatically, simply do not set any width.
As for the automatic vertical adjustment, you can apply a 100% height to the Editor's <table> element. However, in Internet Explorer you will need to adjust the height of the <iframe>'s parent <td class="k-editable-area"> element. Do it in the Splitter's resize event.
If you need further assistance, please submit a new support ticket.
the Telerik team
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