I started working on a modification of the simple zoom shader (reshade.me/forum/shader-presentation/4150-simple-zoom-shader) and came up with this. It allows you to magnify an area of your screen (assumed to be the centre) and display the result within a desired shape and position. Right now it can only be toggled, but I'm looking at ways to allow hold to zoom. This is my first shader so I would appreciate ideas on how to improve it.
Here's some screenshots of different ways it can be used: