Perhaps this feature may be implemented easily by treating a hatch like a polyline, for which "add node" and "delete node" already exist?

Or even simpler: a tool that converts a hatch into one or more polyline(s).

Thanks for the suggestions.

Please note that a polyline in QCAD (DXF/DWG) is defined as a sequence of line segments and arc segments.
A hatch boundary on the other hand may contain line, arc, ellipse arc and spline segments.

Your best option at the moment might be:

1. Select the hatch
2. Use the property editor to change the 'Solid' property to 'yes'.
3. Explode the solid fill: Modify - Explode (X,P) [=> See attached fix for Explode.js that ensures that arc segments are not converted into splines]
4. This leaves you with the boundary elements of the hatch (lines, arcs and possibly splines)
5. These loose boundary elements can be converted into a polyline if they consist of only lines and arcs: Draw - Polyline - Create from Segments

that's just perfect for my use case, thank you!