To delete a previously imported auxiliary file, do the following:
Select File> Auxiliary File Import to open the Auxiliary File Import dialog box.
Select the auxiliary file instance from the drop-down list in the Aux. File Instance field.
Click the Delete button.
Click Yes in the message box asking if you would like to delete the Aux File.
The selected auxiliary file instance is deleted from the 3D PCB Viewer. However, the file itself remains in the design’s database. If you have imported more than one instance of an auxiliary file, you must delete them individually.