For manipulation with image file metadata (reading, editing), the great application ExifTool is widely used, which is also used by the APhoto application itself.
On the ExifTool forum, I asked for additional support for Affinity file formats, see https://exiftool.org/forum/index.php?topic=8151.msg65450#msg65450
However, since it is a proprietary/undocumented format, it will be difficult to complete it.
Therefore, I am asking the Affinity developer/designer to support this request, and to provide information regarding the metadata, which would then be available and usable in ExifTool, from which the APhoto application itself could also benefit.
Thank you