When working with a spreed sheet group cells with the same value, and you count the occurrences.
To group different Jira fields with the same value, one way is to get these values into the new field, and import it as a new dimension.
The values with Jira users are coming from the fields „reporter“ and „assignee“.
Create a new scripted groovy field with the free, and great Jira add-on myGroovy. Choose a groovy user field.
Create two configuration for this custom field.
Add the groovy scripts for the projects, and issues types where it makes sense.
For the reporter.
For the assignee.
Import this field as dimension, and also its properties.