You can customize dashboards using CSS within simpleXML. However, this may change once you upgrade again. To get started, look at these pages:
https://answers.splunk.com/answers/330361/how-to-apply-custom-css-to-a-dashboard.html
https://docs.splunk.com/Documentation/Splunk/7.1.0/AdvancedDev/UseCSS
https://answers.splunk.com/answers/500832/css-reference.html
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