This must be exact on the spot, where it is and need a highway key tag also for routing, on a platform, because of platform, highway=platform?

Important, where it stop and start.

It is not good to say (tag) there is a platform and somewhere on the platform is a tactile_paving, as tactile_paving=yes

I did see the V2 version of public_transport, and was thinking how to fit in highway=platform.