Need to mass delete custom field values

Hello,

It has come to my attention through Wrike support that there is no way to bulk delete the values (content) in custom fields. We have a use case that requires that we capture the person's name and email address who is requesting project support - so that data goes in custom fields for reporting purposes.  However, after 3 years we are required by law (GDPR) for global companies to remove the personal data that is 3 years old.  We must keep the task (historical record of the work), but delete the names and email addresses of the requestors.  We cannot delete the custom fields entirely - because we must continue to capture names and email addresses of our requestors going forward.  We only need to delete the names in the system that are 3 or more years old.

NOTE: I tried this using the table view function that allows you to "delete" the value in the field, and then drag the empty cell value down to delete the contents of the cells below.  Works great, but anyone can click on the gear icon and restore or see the previous content that was there on the custom field in the task.

We cannot go task-by-task to delete this information as there are over 5,000 entries to edit.  And apparently, removing the content of the field is not enough, if it can be restored by any user directly in the field.

Please advise if there is a way to permanently delete the personal information for international legal requirements like GDPR, which mandates the removal of names that are 3 years or older from all systems.