Released around November 2018 for the PC (Steam) version, this update focused on bringing the English release closer to the "definitive" experience by adding missing content and fixing long-standing issues.
If you are looking for information on "updates" to the series as a whole, here is the current status of the Cold Steel arc: The Legend of Heroes Trails of Cold Steel Updat...
: Newcomers are generally advised to start with Trails of Cold Steel I or play the earlier Zero/Azure arc first to fully understand the deep lore and recurring characters. Released around November 2018 for the PC (Steam)
: A single playthrough of the first Cold Steel game typically takes about 59 hours for the main story, reaching up to 108 hours for 100% completion. : The update added 148 additional English voice lines
: The update added 148 additional English voice lines . This was part of a larger effort to bridge the gap between the English and Japanese versions, as the Japanese release originally had more voiced dialogue than the initial Western launch.
The prompt appears to refer to for The Legend of Heroes: Trails of Cold Steel , which was a significant update released to enhance the English localization and technical performance of the game. Update Highlights: Version 1.6