There is no built-in method of doing this on the LMS, however, the administrator who originally enrolled the learner will have a copy of the login details sent to them.
The administrator can simply forward these login details onto the learner manually, and the learner will still be able to log in.
A unique link is not required. They will just need to go to the same login page as the administrator, but log in as a learner.
If you are the administrator, but not the one that created the learner account, you are still able to reset the learner’s password and send it to the learner manually. Instructions on how to do this can be found here: Learner Support - How do I change a learner's password?