It is possible to use PSDImporter to import files with ‘psd’ extensions. The following are the sample scripts that you can use.
using UnityEngine;
namespace UnityEditor.U2D.PSD
{
[AssetImporters.ScriptedImporter(1, new string[0],new[] {"psd"} )]
internal class PSDImporterOverride : PSDImporter
{
}
}
namespace UnityEditor.U2D.PSD
{
[CustomEditor(typeof(UnityEditor.U2D.PSD.PSDImporterOverride))]
internal class PSDImporterOverrideEditor : PSDImporterEditor
{
}
}
After implementing the above scripts, you will be able to switch the importer from a dropdown list in the Inspector.