No, if you have a Fiduciary claim you can't file a Supplemental Claim.
Where can I get more information about Loan guaranty?
You can also ask a regional benefit office for a copy of this form to fill out. Or you can call the VA toll - free hotline at 800 - 827 - 1000, Monday through Friday, 8:00 a.m. - 9:00 p.m. ET