No, the only variable that the candidates can fill in is the [candidate_signature]. As for the rest of the e-signature variables (both default variables and custom variables), they are designed solely for the hiring team to fill in when completing the e-signature creation.
The [candidate_sign_date] variable is automatically populated by Dropbox Sign once each signatory signs the document, the candidate does not need to fill in this variable. The [candidate_sign_date] variable's format is YYYY/MM/DD.
To find out when the candidate signed the e-signature if the [candidate_sign_date] variable is not included in the document, check the audit trail created after they signed.