Customizing which characters are emitted when shift is held for specific keys?

[spaceunifyfifty]

Normally, the key next to the letter M on a qwerty keyboard is , and acts as< when holding shift. I think that is an unintuitive pairing, and I already have < and > on a separate symbol layer so it's a waste of shift functionality. I would like to change the effect of holding shift for this key. I want taps to still give , but tapping the key while holding shift should give . which would also remove the need for a dedicated . key, freeing up space on my English layer and consolidating punctuation to a single key (very intuitive).

There are other keys I want to do this for. I want ? and ! to be the same key; differentiated by holding shift. (/ and ? is a dumb pairing, as is pairing 1 with !, I already have a dedicated number layer)

I looked in the editor and couldn't find a way to customize shift held variation for specific keys. I think this would be very useful for many people, and is something you would expect a programmable keyboard to be able to do easily.

I need a solution that doesn't involve me changing the default functionality of my shift key (like making it a layer toggle), as I still want most of the default behaviors of shift and need shift to be registered on the OS level when I press the key for other daily actions like selecting text in a text box.

Is this already possible in the editor?? If not, are there any significant barriers to implementing it?

[xyzz]

You can use the key overrides feature to implement this behavior, for the example of , => ,, shift-, => . it would need to be set up like this: