Within Recruitment settings, there is an option to allow managers to be able to add and edit candidates. This can be done via the candidate card or through a requisition.
To enable this setting, go to:
Administration -> Company -> Settings -> Recruitment Settings
and adjust the 'Allow managers to add and edit candidates' field to Yes:
Managers will then be able to add candidates by clicking on the 'Add' button via:
Recruitment -> Candidates
and edit the candidates added for any requisition for which they are set as the hiring manager.
They will still be limited in their ability to delete records, move candidates into employment and other recruiter functions.
When the manager clicks on add to add a candidate, he will only be able to add a candidate for the job role for which they are the hiring manager: