> and wondering how easy it would be to create a .osm file instead of uploading the data. The JOSM editor’s todo list plugin would make it easy to plough through all the polygons or centroids, and do any refinement necessary. For example, I’m curious to try this out to detect crosswalks, and those need to be glued to the highway being crossed.

Hi, I didn't know about this possibility. I should have better researched what were the different options. I will be taking a look on implementing this approach.