A toggle that auto-deselects the shape tool after one use, just like the eraser.

A further enhancement would be turning the whole tool into a toggle, which detects and corrects any shapes if it is turned on. This should ideally work with the highlighter alongside the pen. I understand there might be complications on this improvement, so I put the auto-deselect function in the title, as this toggle will suffice to solve the frustration where a circle would appear unexpectedly while writing a sentence.