To create a new custom user view with appropriate fields for an assignment step, what is the quickest way to do this?

The quickest way to create a new custom user view for an assignment step is found in the Case Designer, specifically under the Workflow Tab. This option allows you to directly work on the case structure and associated user interfaces in a streamlined manner.

In the Case Designer, the Workflow Tab is dedicated to managing the flow of work and configuring different steps in a case, including assignment steps. It provides a visual representation of the case flow, allowing you to easily link the newly created user views to specific stages of the case. This integration ensures that the user interface aligns with the business processes and requirements established for the assignment, making it efficient for business architects to manage.

Other choices such as Dev Studio or App Studio involve more extensive configurations or are focused on broader development tasks rather than the specific aspect of customizing assignment views quickly. Admin Studio primarily deals with application administration rather than designing user interfaces for case assignments. Thus, using the Case Designer's Workflow Tab is the most straightforward and effective approach for crafting customized user views directly tied to assignment steps in the process.