I want to add current customer session custom field to the every category url.
lets say if user typed in the browser http://test.html , this should forcefully change to http://test.html?customer_number=1234.
lets say url is http://test.html?color=red ,this should forcefully change to http://test.html?color=red&&customer_number=1234
customer_number
. if it's not set, set it and redirect to the new url: devdocs.magento.com/guides/v2.4/extension-dev-guide/…. But I have a feeling you're doing something wrong. If you want customer specific content, use the session to do that not GET params