Can't assign some types of hotkeys

hey there,
trying to wrap my head around how to manage hotkeys in Blender. The question is - how do I assign Any Left Shift instead of Any Left Alt as shown in the image or is it hardwired deep down in code? When I try to press Shift, it won’t work unless I press another key with this modifier which isn’t what I’m actually after.
Any clues?

A couple more questions - When I last exported my layout, I thought I’d get a bunch of lines with hotkeys next to them (smth like Max does), but instead I got Python code. How do I find where the hotkeys actually are and modify them in a text editor if need be?
Is there a way to assign multiple shortcuts for a single operator?
Also I didn’t notice that Blender would notify me in case the hotkey had already been bound to another operator or have I missed smth?

Thanks