You can conveniently rename a thumbnail's file without using the Finder.
Choose Reattribute- from the Selection menu or press [ R]. The bottom portion of the window is used to edit the selected thumbnail's
file comments. Press [\] for line termination in the comments field. You
must press [ENTER] or [RETURN] to make your change permanent.
You will hear an error beep if the file name is longer than 31 characters,
the comments are longer than 200 characters, another file in the folder
has this file name, or the file is locked or on a locked volume.
Not all versions of the system software preserve file comments when
rebuilding the Desktop database. You are advised to use this feature only
with System 7.5 or newer!