Sprout Import Doesn't Recognize Asset folderPath Property
folderPath is not supported when relating an asset to an Entry but there is a workaround. In your generation script you can call the code below to get the folderId with the given path:

$folderId = \craft\records\VolumeFolder::find()
-&gt;where(['path' =&gt; 'documents/pdfs/'])
-&gt;scalar();