Oh! You mean custom domains (the pencil icon that used to be there)?
The reason that traditional custom domain linking on Replit was removed is because traditional repl.co hosting is being removed from Replit. It is being replaced by deployments (replit.app). You can link a custom domain to deployments. Repls require a paid plan/connected credit card to host but will still be able to have custom domains (so long as the repl hosts a website).
Hope this helps!