Adding a missing landmark to a mrk.json file

I have a point on a bone that i’m landmarking that isn’t present on all the samples in my data set. To be able to run GPA+PCA analysis I need to have a consistent number of points for each sample, so is there a way I can add a “missing landmark” so I can keep the number of landmarks the same, while not impacting the PCA slicer gives me?