I'am trying to import large OSM data to QGis, namely all buildings polygons in Czech Republic. Finally, I imported polygons using PostGIS layer, because everything else had strong issues. See my previous question: Importing large OSM data to QGis failed (using QuickOSM, SpatialLite layer or add vector layer).
Now, I have another problem: some attributes (tags) are missing - probably the attributes, that are placed in relations.
Is there method, how to apply OSM relation tags to it's sub polygons and import them to QGis?
Example: this building (relation): openstreetmap.org/relation/3679169 has interesting tag "building:levels" but PostGIS layer in QGis contains only polygon without it.