labeling problem manipulating .mat file

Hi all, I am using the Ground truth labler app to create .mat file The created file (gtruth) contains just the coordinates of the rectangles around the labeled objects without reference to the name of the image. I want a .mat file similar to the example in trainFasterRCNNObjectDetector help Moreover I can't modify in this file when I export it to .mat file My question is how to add the name of images to the corresponding labeled objects from the ground truth app or how to modify that file.

[Stephen23]

"Moreover I can't modify in this file when I export it to .mat file"

What have you tried? Please show us the code that you used.