It’s not about to reinvent all things and create new arbitrary incompatible GPX types.
Kurviger exports all waypoints (start + via + shaping + end) in “wpt” and “rtept” types.
(names already have their official “name” tag, only shaping points remain to decide)
Instead of add an extension, can better use an existing element, like the “type” tag: Element: type: Type (classification) of the waypoint.
Anyway that is to be discussed in their feature topics:
(but universally without focus on any manufacturer)