The Abbr. field in the More Options section of the source panel provides a short or alternative title for a source.
For example, a source titled "Extracts of Baptisms for the Children of John and Jane Smith, Middleton, Register of Baptisms 1813–1842" could have the abbreviation "Middleton Register of Baptisms 1813–1842". The abbreviated title is used in reports after the source’s first appearance.