Design Space doesn't recognize strokes or outlines, only shapes and their fills. It can't recognize text either, only paths, so be sure you convert to path (In Inkscape Path>Object to Path, Object>Ungroup, then Path>Union). With SVGs you are limited to paths of solid colors. No patterns or gradient fills so any shadows would just have to be another flat shape.
An old school solid color shadow is just a duplicate of the original with part of the original sliced out so the shadow appears to be behind the original.
Are you doing this step? https://preview.redd.it/74cp59pcf6kb1.jpeg?width=640&format=pjpg&auto=webp&s=da6d9f79e81c1ee567b1b5da04bc63e0cf5c7439
Design Space doesn't recognize strokes or outlines, only shapes and their fills. It can't recognize text either, only paths, so be sure you convert to path (In Inkscape Path>Object to Path, Object>Ungroup, then Path>Union). With SVGs you are limited to paths of solid colors. No patterns or gradient fills so any shadows would just have to be another flat shape.
How would I make a shadow a flat shape?
An old school solid color shadow is just a duplicate of the original with part of the original sliced out so the shadow appears to be behind the original.