https://www.epo.org/en/node/can-form-ep1038e-be

Can Form EP(1038E) be used by any party to the appeal proceedings other than the appellants?

Yes, Form EP(1038E) can be used by any of the parties to appeal proceedings. The role of the party concerned will be clear from information contained in the letter and/or the accompanying document(s) being filed. The Names section can be left empty. If, however, you enter data in the Names section, not all of the relevant name categories are available; the EPO Boards of Appeal are aware of this. If the party to the proceedings is represented, the name of the party's representative should be entered in the relevant section.