Yep, I read the below in the help files. So the next question is, whether you are using a custom field for Short title rather than the one in the ref types or something else.
I think it is something else. I looked at Turabian footnote. It has an option to not show the title unless needed for disambiguation. So in secondary citations it didn’t show any titles? Whether or not there was a title or short title?
See attached image for footnote settings. Removing that tick box results in either the short title or the title if there is not short title, in being included in the footnote.
so in below, Greaves citation has a short title and Gilbert doesn’t.
with that checkbox checked:
[1] M. F. Greaves, Cancer: The Evolutionary Legacy (Oxford, New York: Oxford University Press, 2000).
[2] Scott F. Gilbert, Developmental Biology, 9th ed. (Sunderland, Mass.: Sinauer Associates, 2010).
[3] Greaves.
[4] Gilbert.
and with it unchecked
[1] M. F. Greaves, Cancer: The Evolutionary Legacy (Oxford, New York: Oxford University Press, 2000).
[2] Scott F. Gilbert, Developmental Biology, 9th ed. (Sunderland, Mass.: Sinauer Associates, 2010).
[3] Greaves, Cancer.
[4] Gilbert, Developmental Biology.
Short Title
Use the Short Title field to enter abbreviated versions of the regular title which should be used as part of an in-text citation or a footnote citation. This is a common request for many of the humanities styles which use a shortened form of the title in the citation to help identify which reference is being cited. For example, MLA typically lists just the author name and the specifically cited pages in the in-text citation:
(Perin 141)
But if there are multiple works by that author, MLA requires that the title or a shortened form of it be added to the citation. If the full title of the reference is fairly long, such as Burning the Midnight Oil: Tales from Working the Night Shift, you should enter an easily recognizable form of the title that starts with the first word on which the normal title would be sorted. For example:
(Perin,Burning141)
If an EndNote style is configured to use the Short Title field, and that field is empty for a particular reference, the normal Title field is used instead.