Edit IPTC/XMP tool - keywords

[orbspider]

Small thing to report but it's something that could be improved.

In the Edit IPTC/XMP tool, Keywords tab, why is there need for checkbox "Use parent keywords"?

At present usage is:
To add a parent keyword to the list this box must be checked, and then child keywords can't be added.
To add child keywords this box must be unchecked and then parent keyword can't be added!!

This usage seems unnecessary.
If we select a parent and click the [^] button we expect a parent keyword.
If we select a child and click the [^] button we expect a child keyword.

Is that right?

[xnview]

you can double click on a parent keyword