MATNWB How to handle nested structs

[JustinKillebrew]

I have an NWB file created with a PYNWB converter containing multi-session OpenEphys data. There are several mat files that contain metadata, behavior data, and initialParameters. My problem is that many of the fields are nested structs/cells and I don't know how to handle them.

For example:

>> PDS.data{1,1}

ans = 

  struct with fields:

              behavior: [1×1 struct]
              datapixx: [1×1 struct]
                pldaps: [1×1 struct]
              stimulus: [1×1 struct]
                reward: [1×1 struct]
            postTarget: [1×1 struct]
                   ITI: [1×1 struct]
         flagNextTrial: 1
                iFrame: 644
                 state: 16
              keyboard: [1×1 struct]
     currentFrameState: 1
                timing: [1×1 struct]
                    mp: [1×1 struct]
             userInput: 0
         unique_number: [25 3 6 15 56 45]
               trstart: 1.7413e+09
                 ttime: 5.3763
         nextFrameTime: 5.3759
                  eyeX: -8.5670
                  eyeY: -397.9062
                 pupil: -5.0532
    remainingFrameTime: -3.8721e-04
              trialend: 5.4763
           trialnumber: 1

I'm creating a TimeInterval for each of the mat files to store as an Interval in the NWB:

% add the mandatory start/stop time
fieldNames = ['start_time', 'stop_time', fieldnames(PDS.data{1, 1})'];
numFields = length(fieldNames);
    
% create a new TimeInterval with the fieldNames as colnames
trials = types.core.TimeIntervals('colnames', fieldNames, 'description', fname);

Unfortunately, some of the fields are structs and I would need to add column names to the table but not all the elements would use them. How would I add column names after creating the TimeInterval? What is the best/correct way to handle this?

Thanks,
JK