When you add a route to OSM, it is not immediately available on the map. But BRouter has the data a day later. The LoRouter (BRouter) makes an update every 7 (4) days. I think you can also add the data manually.
About routing: You can trace the route in the route planner and all parts where there is a path are automatically routed. If there are areas where there is no path, then you add a manual segment. Quick changeover: press and hold Routing profile.
Turn-by-turn directions are not yet possible. I change the shaping point before the manual segment to a via as a turn-off hint. You can also name the via Attention, so that it indicates the area you want to look at in particular. The name of the via is announced during navigation.
About routing: You can trace the route in the route planner and all parts where there is a path are automatically routed. If there are areas where there is no path, then you add a manual segment. Quick changeover: press and hold Routing profile.
Turn-by-turn directions are not yet possible. I change the shaping point before the manual segment to a via as a turn-off hint. You can also name the via Attention, so that it indicates the area you want to look at in particular. The name of the via is announced during navigation.