Custom added XMP metadata locked in metadata panel; how to modify?

[iamjwk]

With ExifTool I created new metadata tags, for example:
   XMP-VideoInfo::VideoEditingDetails
I created my own new XMP tag group "XMP-VideoInfo" and added new tags to it.

I can set/read these with ExifTool. The video file with this metadata tag set loads fine in IMatch and the content is shown in the metadatapanel.

BUT it has the lock icon and states "This field is read-only and cannot be modified". 

How can I enable editing my own custom metadata tags?

Regards,
Jan-Willem

[Mario]

Creating your own tags, why?

If IMatch shows the lock icon, the tags are reported as read-only by ExifTool. This is where you should start to find a solution. How did you create your own tags for ExifTool, how did you define them? Custom configuration file for ExifTool?
IMatch does not know anything about your custom metadata tags. It imports them, probably. But when ExifTool reports them as non-writable, that's how it goes.

ExifTool and IMatch support about 15,000 metadata tags. I'm not sure I understand why you would want to create your own tags on top of that. Or how you plan to transfer your custom tag definitions to IMatch.
There is only on configuration file for custom non-standard tags, and IMatch uses that already for the custom legacy IPTC tags implemented by classic tools and related tags required by popular stock photo agencies and services.