Anyone know how merge a dict into a dict array?

I'm currently working on a polyphonic sequencer for max and I'm managing the data using a master dict object. It's the first time I've used dict and it is taking a while for me to get my head around.

In the patch below I think I'm creating an array in the master_data dict. I'm able to address the different patterns individually in a sub_data dict but when I alter a pattern I'm not sure how to get that back into the master_data dict? I could step through the data and replace it but I imagine there must be a simpler way of doing it that I'm missing.

Any help would be greatly appreciated!

Here's an Instagram of patch I'm working on