The Plan Specifications do not permit this. Only the Promoter (CaixaBank) can make contributions to the Plan.
Allowing this would represent a potential reduction in CaixaBank’s obligations insofar as the risk benefits (disability or death) are covered in the first instance with the vested rights of the participant.
If you want to make private contributions to a pension plan, you can use the Associated Collective Plan (type 302), which is managed according to criteria and policies very similar to those of the employment plan.