I wanted my chain heal tracing just to be the "border" widget. In order to achieve this I had to remove the texture path from "healfeedback" widget, otherwise the corner texture would always be there though I disabled "healfeedback" widget. Seems like the heal trace is forced to be using "healfeedback" widget (in addition to the one configured in the spell list) and disabling that widget didn't seem to do anything to my heal tracing.