If there's a sort-of-selection widget, that's a grid of options - and upon activating one it acts like a button and opens a new modal flow - what is that? What is it called? Is it an existing thing?
Currently you have to tab through all the buttons in this grid to get through it and out the other side. So I think it needs roving tabindex.
I also think it should probably be navigable in two dimensions with arrow keys, like you'd expect in a calendar date picker.
