Dynamic way to build individual endpoints for each users within Appian

What kind of "endpoints" are you looking for? Can you elaborate on your use case?

Use a single dynamic endpoint (e.g. /users/{username}) to fetch any user's data instead of creating separate endpoints.
The API extracts the username from the URL, queries user functions and returns JSON.
This approach is scalable, secure, and low-maintenance -> no updates needed when users are added or removed.