To clarify...

Manage / Users : individual accounts that can have multiple wallets

Extensions / Pay Links : individual lnurlp configurations that can be mapped to wallets that are associated with users.

Its the pay links that let you set username in the /.well-known/lnurlp/{username} and you set allowable amiunts, enable comments (by character max), any webhooks for payment completion, and nostr zap support