enhancement
The instance exporter currently exports everything for which it cannot find an instance resolver. However, this is generally not useful, as it leads to an export also exporting master data of the application - and then re-importing it again (as a duplicate) if you have forgotten to configure a suitable instance resolver.
In this case, it is better not to export the reference (and to log an appropriate warning). You can then decide whether a resolver is missing or whether the reference needs to be excluded.
Improvement
When exporting, it must be explicitly specified which references are to be included (treated like compositions), or the references must be excluded if they point to objects that are not part of the export.
Accordingly, the import must be able to process forward references, as it is not yet possible to determine whether the referenced object is also exported when exporting a reference. The export only exports objects to composition references or explicitly included references.
With two new TL script functions, the export and import can also be used via TL script: instanceExport() and instanceImport().