The routing helper should display a top panel with button controls that allow you to step through the relation members.
When stepping to the next member, the map zooms to that member.
There are four buttons: to previous gap, to previous member, to next member, to next gap

For the time being I think it's enough to only step through the members that have an empty role. The platform and stop members would then come later for the transport modes that have stops and platforms.