Let's say you have created a Categorical Dropdown to filter your charts by User Id. However, you want to select the User Id's associated User Name from the dropdown instead.
To create a Categorical Dropdown with a key-value pair, simply open your Categorical Dropdown for editing and drag a second column to the Dimensions section.
The first column's values are used to filter charts, and the second column will be the display values.
To display User Name values in the dropdown, and filter by their associated User Id, this is what our preview looks like:
When setting key-value dropdown default values or report values, use the key (first column), not the value (second column).
For more information on creating Categorical Dropdowns and other Dashboard Variables, see our documentation.