The place of the sorting button is aligned on the left side of the Textbox and vertically centered by design. It cannot be re-aligned in the viewer as all items are having absolute positioning. In your case, to reduce the space between the button and the text, you can set text-align left and vertical-align middle to the textbox.
Do you want to have your say when we set our development plans? Do you want to know when a feature you care about is added or when a bug fixed? Explore the Telerik Feedback Portal
and vote to affect the priority of the items