On the keyboardio wiki introduction page, it says
It is possible to make SHIFT + 4 create a character other than “$” in the firmware by enabling a plugin called ShapeShifter:
It’s probably better to consider that an advanced option, and try a more straightforward approach first.
If you want to change the shifted character on a key, look in the sidebar for the link to the Keyboardio forum; there are discussions on the forums about how to do it, and friendly folks there who can answer questions.
I’m wondering why that is, because I certainly want to alter many shifted characters in my setup, and the instructions given its use are not all that intimidating. Are there issues about it that mean it should be avoided - I’ve been seeing it proposed pretty freely in the forums? Also I couldn’t find the quoted discussions of simpler methods.