One option would be to use a zero.
I made a custom text column in one of my libraries to get around that problem. I wanted to name it Series but calibre did not like that since it already had a column named Series. I got around that by naming it Series with a space in front of it. When displayed, the space is not noticeable in the column heading. Now I have a Series column with no numbering. One could manually add numbering to a column like that if one wanted some series unnumbered and others numbered or put the numbered series under an unnumbered series heading and the numbered names in a numbered subseries column.
Last edited by Lady Fitzgerald; 10-17-2010 at 02:04 PM.