I am wondering if there is a way to scale SVG files I have stored as blob in a Spatialite database according to the current zoom level in QGIS. My hope is to have the SVG icon resize itself when the map is zoomed in/out. I understand there is a size option in the data defined option, but it does not seem to provide a dynamic sizing option. I am open to options.
If you have an SVG Marker symbol layer, you can set the size units to map units. That way the icon will always have the same real-world size.
Note that the size in the data-defined properties is not radius or diameter but area - which I find weird and might be considered a bug.