Is there a way to change the default value for shift+arrow increments, when editing?
The API refers to keyboardIncrement as a way to change the arrow increments, but I can’t seem to find how to modify the shift+arrow values.
It feels like I’m missing something right in front of my nose.
I believe you are not missing anything. The Shift increment cannot be reset separately, currently. Will be adding something to that extent soon.
Wonderful, I’d also appreciate being able to adjust this increment.
That would be quite helpful, as changing (only) the most granular increment isn’t super useful in a lot of instances. Is there an ETA, or is it just soon™? 
I cannot give you a date, sorry.