Who this is for: Admins. Custom field mapping for sync is restricted to Admin users.
Beyond the standard system fields, you can also sync custom fields between candidates and contacts, like a custom Industry Focus field that should mean the same thing whether you're looking at someone's candidate profile or their contact profile. You can set this up two ways: from CRM Settings, or right where you create the field.
Before you start
Field Sync needs to be enabled under CRM Settings → Sync Profiles. This option won't appear otherwise
Mapping a custom field
Go to CRM Settings → Sync Profiles under Settings
Click on + Add Custom Field button
Under the Candidate fields select one from the dropdown, and then choose a custom field of the same type on the other entity
Click Save
Example
You create a single-select custom field called Practice Area on the Candidate entity. While setting it up, you map it to an existing Practice Area custom field on the Contact entity. From that point on, picking a value on one profile updates the other.
Things to know
You can only map a custom field to another custom field of the same type. A single-select field can't map to a text field, for example
A mapping created here also shows up under CRM Settings → Field Sync, and vice versa. It's the same mapping, just two places to manage it from
If the available options don't match between the two fields, see Candidate-Contact Field Sync: Limits and Known Behaviors for how new options get handled
This option only appears once Field Sync is turned on in CRM Settings. If you don't see it, sync likely isn't enabled yet