How to display grid field with CDT having nested CDT

I have a process backed record interface with a OMCAppointmentInfo CDT which has AppointeeTM CDT array. Each OMC Appointment will have multiple TMs. Trying to display TMs fullname for each Appointment and no data is being displayed. Below interface code doesn't display any data

a!gridTextColumn(
label: "TM Appointee",
field: "OMCAppointmentInfo.AppointeeTM",
data: index(index(index(local!datasubset.data.OMCAppointmentInfo,"AppointeeTM",{}),
"AppointeeTM",{}),"FullName",{})
)

here is the sample AppointmentInfo CDT data:

[AID=1241, AwardNumber=CORHQ-15-A-0022, VendorInfo=[AID=1259, Company=% OF COMPLETION INSPECTIONS, Address=12051 ANDES ST., City=RENO, State=NV, ZipCode=89506, POCName=Meena, POCEmailAddress=mrajagopalan@fdic.gov, PPID=268454006], AppointeeOM=[AID=1199, FullName=Meenakshi Rajagopalan, UserName=mrajagopalan, DateAppointed=1/6/2020, DateSigned=6/23/2015, DateApproved=6/23/2015, DateRemoved=, Signature=PS, APSModNumber=, AdditionalDuties=If you are appointed as a Task Order Oversight Manager (TOOM), you are required to communicate and work jointly with the individual appointed as Oversight Manager (OM) for the Agreement (i.e. Basic Ordering Agreement (BOA) Receivership Basic Ordering Agreement (RBOA), or Blanket Purchase Agreement (BPA)), to ensure consistency across the Agreement. Decisions or guidance that could impact other Task Orders will be coordinated through the Agreement’s OM., Deleted=, PPID=268454013], AppointeeTM=[AID=585, FullName=Mirek Kiczko, UserName=mkiczko, DateAppointed=5/15/2015, DateSigned=, DateApproved=, DateRemoved=, Signature=, AdditionalDuties=test2, Deleted=, PPID=268454043],[AID=586, FullName=Michael Chirlin, UserName=mchirlin, DateAppointed=5/14/2015, DateSigned=, DateApproved=, DateRemoved=, Signature=, AdditionalDuties=test3, Deleted=, PPID=268454027],[AID=587, FullName=Braden Jaeger, UserName=bjaeger, DateAppointed=5/15/2015, DateSigned=, DateApproved=, DateRemoved=, Signature=, AdditionalDuties=testing, Deleted=, PPID=268454037], AwardCO=mrajagopalan, Division=Division of Administration, EffectiveDate=5/31/2015, ExpirationDate=5/31/2015, ClosedOutDate=, Description=Test Solicitataion, APSObjectDBID=2427, APSObjectPPID=268453989, PPID=268454006]

It has to display the 3 TM Full names . Any ideas hot to achieve this?

Thanks,

Meena