Yes, the same signer can affix multiple digital signatures within the same envelope. If the different signatures requested from the same signer are of the same type (e.g. signatures with a OTP SMS), when creating the envelope, the sender can choose whether to request that each individual signature field be signed or whether to allow the signer to sign all their assigned fields by means of a single operation (Multi-signature function).
Further information on the types of signature that can be assigned to signers can be found here:
https://confluence.namirial.com/display/eSign/User+Guide#UserGuide-(2)Designer