I am using author citations along with a List of Abbreviations in order to cite the same works by the same author repeatedly throughout a book-length text. Often I add italics to point out specific meaning within multiple-line quoted material. Can I abbreviate the "emphasis added" that I am including within the citation parentheses? Is there a convention for such an abbreviation and does it make sense within a non-fiction book within the field of philosophy?
On the other hand, Google Ngram Viewer is unfamiliar with the abbreviation, so overall it must be quite rare compared to the unabbreviated phrase.
I would discuss using this or another abbreviation with my editor or publisher.
A good practice seems to me to spell the phrase out the first time you use it. There are similar phrases with similar abbreviations (e.g. "emph. supp."), and your readers may not be familiar with (all of) them.