Version: 2020.2
public string[] overrideFileExtensions ;


List of file name extensions (not including the leading period character) that the scripted importer can handle in addition to the default file name extension(s).

You can change which importer to use for an asset by (a) selecting the importer from the Importer drop-down menu in the AssetImporter Inspector; or (b) via scripting with the AssetDatabaseExperimental.SetImporterOverride method.