Google has updated the short_title attribute specifications in the Google Merchant Center, indicating it will now be used not only for Demand Gen campaigns but also for visual formats like YouTube and Discover within Performance Max campaigns. Previously, the help page stated that short titles would only be applicable to Demand Gen campaigns.
The latest update also specifies that merchants should now aim for short titles under 40 characters (with a maximum of 65 characters) to avoid truncation on mobile devices.
Read the official announcement: Short title [short_title].
This update was uncovered by Hana Kobzová.