You are trying to update several tags for Customers and Contacts, but the field 'Tag' is not showing up in any template from Data Workbench, Migration Tool or Mass Data Maintenance.
SAP Cloud for Customer 1802 and higher.
Reproducing the Issue
Go to the Customers work center.
Open Accounts view or Contacts view.
Search for any account or contact and open it.
In the header, scroll to the bottom and look for the '+' icon, to add a tag.
See there is no option to mass update tags.
Currently it is not possible to mass update tags in the Customer/Contact screens, neither by using Data Workbench, Migration Tool or Mass Data Maintenance. Tags are specific to each user and specific to each object.
This is the expected system behavior.
Tag, Mass Update, Upload, Data Workbench, Mass Data Maintenance , KBA , LOD-LE-BP-BP , Business Partner , Product Enhancement