Modifying the route is not possible (or safe) while navigating.
Stop navigation via long press (not pause), then plan a route.
For more details please see the documentation:
- Kurviger PRO: Navigation, Simulation, GPS Recording, Screen Lock, Rerouting, More, Offline use [Kurviger Knowledgebase]
- Kurviger PRO: Navigation, Simulation, GPS-Aufzeichnung, Displaysperre, Rerouting, Mehr, Offline-Benutzung [Kurviger Knowledgebase]
And this discussion: