Modify query param in pre-request script

to add query params there is 2 ways

pm.request.addQueryParams("auth_username={{username}}")
pm.request.url.query.add("auth_password={{password}}")

you can loop over pm.request.url.query it is an array of objects, every object has 3 properties

{
     disabled: true, // only if it is disabled 
     key: "auth_username",
     value: "{{username}}",
}

you can find what you are looking for and set it like you wan’t