What is the recommended way to store and track external URLs in work items?

I need to associate several external resources with work items in IBM Engineering Workflow Management and keep those references manageable over time.

For example, one of the external resources might be to an external website while other work items can contain links to documentation, partner websites, or project-related services.

What is the recommended approach for storing these URLs? Should I use a custom attribute, add them as related links, or use another built-in mechanism?

I would also like to know whether external URLs can be exported together with work item data and preserved when projects are migrated between environments.