Pevara

There is in fact a very easy way to resolve this whit-in Affinity Designer. The real issue here is that the "placed" icons are treated as "Embedded Document", but that can be easily resolved by exporting the document to svg, and re-opening that new svg. This forces the embedded documents to become ordinary layers, with their names preserved, that can be converted to assets in the usual way. It may not be ideal, but at least it scales well and requires zero scripts or regexes.