Hi Mike, I've just noticed this bug report:
https://github.com/mate-desktop/mate-applets/issues/388 It's been closed, so apparently the problem can be worked around by manipulating the XML. Of course, itstool still needs to be fixed. So far, there is no response on either the RedHat bug or on the respective GitHub issues. There is a new itstool version available, but it only includes the fixes that we've had available as long as this bug has been open. Best regards, Lars