Sounds like you want to remove a sender from the Safe Senders list without adding them to the Blocked Senders list. i.e. They are not on either list?

Details will depend on your platform and Outlook version. e.g. see below for most desktop Outlooks.

But you should be able to also just add them to the Blocked Senders list and then remove them from the Blocked Senders list. However that is done in your Outlook version.

Redirecting

Block or unblock senders in Outlook - Microsoft Support