The built-in visualization tools can't really do this for you.
You can likely do it with the Splunk Web Framework, which uses Django and multiple externally available visualization libraries for doing more complex and dynamic charting.
If you want something vaguely similar, you might want to look at doing a chart split by Username, and then do a Column chart with the Formatting options "Multi-series mode" set to "Split" It might be unideal, but it may be something close to what you need.
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