You can use the file browser in the Export Image menu to remove image files, including soft-imported image files, from the filesystem.

To remove media files:

1. Open the Export Image menu.
2. Display the directory containing the files that you want to remove.
3. Select the files.
4. Click Remove, then click confirm.
   NoteIf you remove soft-imported files, the source media is not deleted; only the reference to the clip is deleted.