What is the current wisdom for changing the format of date/time metadata in a column (which currently displays for me with seconds, which I don’t want, now that Mac OS no longer allows the configuration of short, medium and long date formats in its System Preferences?
The Date Added/Created/Modified/Opened/Due columns of List views automatically choose the most suitable format depending on the width of the column. Or are you referring to custom metadata or other views?
Custom metadata.
This depends only on the chosen format in Settings > Data, either a date or date plus time. As such date columns in List view are editable (and likewise the controls in the Info > Data inspector) the format isn’t customizable currently.