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Location in Wordpress:
/wp-content/plugins/configbox-customization/assets/app/data/customization/assetscss/custom.css
Location in Magento 2:
/app/code/Rovexo/ConfigboxCustomizations/view/base/web/css/custom.css
See this article about installing the Magento 2 customization module.
Tips:
Use conventions for rule selectors
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