[Geoff Bacon]

Just put the number (e.g 3 digits, 072) in one of the fields and enter the song number in the filter (it matches in any field).

You could use Song Id as the field but this would need to be a unique number (this field is used when synching the libary to another library) so might be an idea to use Custom (and rename it to something else)

You could also use custom formatting to display the number on the Setlist, Collection and Songs screens.

Geoff