You can try this API call through Postman and it will remove the account from IDN, but not actually delete the account on the source, meaning it will behave like the previous remove account option.
POST https://<tenant>.api.identitynow.com/beta/accounts/<account id>/remove
Additionally, here is a thread about this functionality being removed:
This is the main thread where they mentioned adding this functionality back to the UI at some point: