HI David. You are correct, you can either select each agent individually or select all and view it as a whole 
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What you want to achieve isn’t in the report at the moment, can you add this as to the Ideas Portal using the Ideas tab at the top. This way it can get full visibility and others can upvote the idea.
In the mean time there is good news if you want this information right now using the Reports API and either Excel or MS PowerBI (I have tested this and it does work very well).
I did this using the Interactions Report and then building a report with Activity Codes and Agents.
I can then use the Filters on the side to filter on the Agent to display all their Activity Codes
Or the Activity Codes to show the Agents
Of course it would be great to do this within Liberty Converse but if you can’t get the data straight out of the templated reports provided, you are able to use 3rd party tools and pull data in using the Reports API, you can find out how to do this from within this blog post: Hints and Tips - Using the Liberty Converse Report API
Hope this helps and look forward to seeing the idea logged within the ideas portal.
Many thanks.
Jonathan