The Distance and Direction widget has a bug in WAB DE 2.12 - it does not disable the web map popup's click handler.
I enable all popups by default and configure the popups for my parcel layer in the web map. Creating a line for example and clicking a start and end point triggers popups which I know will confuse end users.
On this note I would suggest a slight adjustment to symbology, for the hollow black circle for the start and end point when you start drawing a line. I'd go with red or another brighter color for the circle, or better yet perhaps a ring with a cross in the middle, like markers on survey and CAD site plans, that is familiar to engineers and surveyors (like the well symbols or boring point for drilling). I do like how it turns in to a circle and cross to show start and end clearly; though you have to notice that; I'd also recommend putting a little 'legend' of what those symbols mean in the widget, that shows after the drawing completes and shows in its panel, since someone may want to screenshot and print; and also also insert a 'title' in to the node element for the start and end symbol so if the user hovers over each one it says 'start' and 'end' respectively, for each symbol node. I add HTML title tags on various elements in WAB. Tooltips are perfect for things like this.