Hello @netops​ 

What do you mean by "URL for a link"?

Like when you are sending content and that content needs to have a link to something that is different for each contact, so you want to build it up by using custom attributes that hold those differences? You can do it by adding attributes in the content as dynamic elements.

Looking at what you have the URL would be something like (depending what you base_url is):

https://www.yoursite.com/{{custom_data.base_url}}?query={{custom_data.query_params}}

You need to tell me more in order to help you out...