text: The online map renderer https://www.hkmaps.hk/viewer.html has a sidebar that can adjust image opacity for map cross-referencing.
  
  Not knowing how to overlay this onto "editing software" (um, JOSM?) is imo a non-issue because afaik both iD and JOSM can specify the OSM Carto rendering itself as the "imagery", and then we can do some intense eyeballing to determine where the mentioned features should be located in OSM.