It is possible to add individual learners to offerings in Ilios. This infrastructure has been in place for a while now. Some of the functional areas of review are missing; but still if you need to add an individual student to an offering, it is possible. As mentioned, the review options are currently limited at best but will be enhanced in the future.
Perform the search as shown below and click on the name of the person to add to attend this offering.
NOTE: Currently the only place to review and verify this addition of individual learners to offerings is in the offering editor. This will be updated soon.