Can you revise an existing .slddrt (format) so the changes will update automatically when an old drawing is opened up? I am assuming the .slddrt file is saved with the same file name.
The sheet format is stored in the file, and ASAIK it only updates when you "reload" it through the sheet properties window.
Welcome to the forum. No, updates to a sheet format will not be automatically reflected in existing drawings, or even in new drawings using a drawing template that contains the updated sheet format. See What's the difference between a sheet format and drawing template? for more information.
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