Creating a new tag for json data... and max len

[qbit]

What would be the command to create a new tag (I am assuming XMP) to for text (json), and, if so, how large can that tag be?

The goal is to copy ALL a photos metadata into a another tag--i.e.create a backup--so I and others can CRUD the other fields.

I am prioritizing (no) sidecars, but I would also like to add my own history tag(s) (Timestamp,Editor).


 

[StarGeek]

There's no command to create a new tag.  You have to create a definition for your new tag.  From there, you would either save it as a separate config file and use the -Config option to activate it or you would add it to your .exiftool_config file.

Creating an XMP tag would be the best, as this quote from Phil says about the size

ExifTool doesn't impose any length limitation on PDF or XMP metadata.

See the example.config file for details.