Honestly, that's a big thing you ask, because pretty much all the abandoned railroad tracks in Greece can be used for hiking trail, and I don't think it's proper to do this just for Komoot to be able to recognize it (in other words, "tagging for the app"). Personally I don't agree with this suggestion, but it should be forwarded to the rest of the community for discussion.
Also, welcome to Argolis and Arcadia :d.