Enable to export custom tag in a csv file

[Spiro]

Hi,
I use XNVIEWMP for un long time but i'm new on this forum, sorry for my english.
I created a custom tag (with exiftools) for all my photos. The tag is correctly displayed in XNVIEWMP GUI (in XMP tags), but when I export tags in a file, this one is always empty.
Can anyone help me?
Thanks

[xnview]

when you export categories?

[Spiro]

Non when I export all tags file of a directory with the menu "Create / List of file"
Thanks

[xnview]

what do you use?