Which of the following cannot be defined or set through a Catalog UI Policy?

The correct choice centers around the limitations of Catalog UI Policies in ServiceNow. Specifically, while Catalog UI Policies can manage specific variable attributes like making them mandatory, read-only, or controlling visibility based on other criteria, they do not apply universally across all form views.

This means that when a requirement is applied through a Catalog UI Policy, it is confined to the specific conditions established for that policy and the view it is associated with. Each form view can have unique settings, which means a requirement effective in one view may not translate to others. Therefore, the concept of applying a requirement across all form views goes beyond the capabilities of individual Catalog UI Policies.

On the other hand, making a variable mandatory or read-only is directly achievable through these policies, as is controlling the visibility of a catalog category. Each of these actions affects the user experience within the defined parameters of the specific catalog item or request, but generally remains restricted to the context of the UI policy itself rather than applying broadly across multiple views.