delete keywords from manager

[BSPicture]

Under Keyword Sets, "wrong" keywords (e.g. with typos, singular instead of plural) are displayed in the manager.

XnView_Delete keyword.png

These wrong keywords make it difficult to assign the correct keyword to an image.

How can I permanently remove these unwanted keywords from the manager?

Additional question: It is possible to record a keyword with identical name several times (the names do not differ by spaces at the beginning or at the end). Is this a bug?

[xnview]

you need to delete them from the categories hierarchy panel

[BSPicture]

That's it. Thanks for that.
My workaround was to delete the XnView database, but the method via the category list is easier and more effective