Metadata Template for a "complex" tag

[BanjoTom]

I have built many Metadata Templates to quickly fill in some of the common tags in the Default metadata panel.  Today I tried to do that for the field labeled "Description Writer," which is more fully identified as XMP::photoshop\CaptionWriter\CaptionWriter\0.   When I tried to put that tag into the metadata template I was building, I got the "Complex Tag" error message, attached to this post.

Two notes about this:
1. In the error message itself, the word "individual" is misspelled.  That is, of course, a very minor issue . . .

2. Much more important: How does one "write to the individual elements" of a tag like this?  I searched the Help file, but did not find or perhaps understand any method to do this.  All I want to be able to do is quickly tag a large group of images with my own name as the "Description Writer" and I assumed I could just create a Metadata Template for that purpose.  Help! 

[Mario]

I've fixed the typo.

For information about how to update XMP tags which are actually structures of nested elements directly, I suggest you refer to the Adobe XMP documentation and the information on the ExifTool web site. It is very important that you do it right or you will break the metadata and may make it unreadable. Some applications may even refuse to load the file afterwards.

I also cannot find XMP:photoshop\CaptionWriter in IMatch. i can only find XMP:photoshop\DescriptionWriter. I think this is what you mean?
DescriptionWriter is the name used by Lr.

On the other hand, I cannot find DescriptionWriter in the XMP spec from 2014, only CaptionWriter. Maybe they have renamed it in the mean time. Or it's a different tag.

ExifTool/IMatch split complex tags like this into individual tags. photoshop CaptionWriter is defined as data type "Proper Name" in the "XMP SPECIFICATION PART 2
ADDITIONAL PROPERTIES" documentation. This is basically a string. Why ExifTool flags this as a structured tag, I don't know. I just work here. When IMatch sees the "complex" option setr in a tag, it displays the warning you see.

[BanjoTom]

Thanks for your quick and helpful reply, Mario.  I'll read up on how to deal with this in the sources you suggest, though it's not a terribly high priority for me . . . It would be nice not to have to enter my name individually for the many images --- but not ALL -- for which I am the "Description Writer." 

[Mario]

It would be nice not to have to enter my name individually for the many images

When you select all files for which you want to add your name in a file window and then just enter your name into the appropriate tag in the Metadata Panel, this tag (and only this tag) will be written to all files.