question - read XMP custom tags

[Uwe]

Hello,
perhaps I didn't find it in the documentation. Is it possible to use so-called 'custom tags' created some time ago via Exiftool, e.g.
XMP-abcde
    tag_text
via IMatch variable/tag and display it in my own layout panel?
Greetings, Uwe

[Mario]

Custom tags are very rare. Especially in XMP. They usually cause issues over time.

In order to support custom tags, they must be explained to ExifTool via a configuration file. This configuration file then must be provided to ExifTool for every operation as a command line parameter. Only one configuration file can be used AFAIK.
IMatch uses it's own configuration file already to manage certain legacy IPTC tags used in new business and to control certain aspects of ExifTool. You would have to add to and maintain your custom tags to this configuration file for every IMatch release. I don't think this is a sustainable workflow.

Adding features like including a user-provided configuration file automatically with the IMatch ExifTool configuration file could probably be implemented. But that would be way to expensive and generate another maintenance debt for probably less than a handful of potential users who would ever need such a thing.

I would suggest you use ExifTool to move the data from your custom tags into one of the hundreds if not thousand tags provided by the standard XMP, IPTCXMP and IPTCExt, XMPMM or similar namespaces. Or ask Phil Harvey to add support for your custom XMP tags into ExifTool.