Hi Patric,
Thank you for contacting us.
As per my understanding, you want to mask the address in the Address Usages panel highlighted in the attached snap-shot.
The field displayed under this panel is in tree format which does not have an F1 help and therefore cannot be configured for masking.
Such fields are not in scope of the masking solution.
Please feel free to get back to us if you have any further queries.
Regards,
Rashda