Hi Emar,
You cannot see more than the top 5 field values when you hover over a field on the left side of the Discover page. This is not possible to change without making changes to the source code.
To see more field values, you can click Visualize at the bottom of the top 5 values.
This will redirect you to the visualization and change the size from the Bucket section to the number you would like to see. Check the example for reference.

For the data you work with regularly, you can create custom dashboards for the top 20 or 50 values so you can access them quickly.
You can follow this document to create a custom dashboard.
https://documentation.wazuh.com/current/user-manual/wazuh-dashboard/creating-custom-dashboards.html
Let me know if you need any further information on this.