If you would like to clear or delete the contents of a specific Tag for a set of references, you can do so in Datarama.
Generate a report containing the references for which you would like to clear the Tag. This can be done for an entire Level of reviewed references, just references that fall within a specific RefID range, all references, etc..
Once the report is generated, scroll to the bottom of the report and click the Add Tags/Labels to References button. In the "Add Tags" field, enter the name of the Tag and following the correct format for tagging references, leave the Tag field as "blank". If you wanted to clear the "Volume" Tag, your entry would look like this:
Then, click Add Tags/Labels. The Tag will now be blank for all references included in the report.