I also wish for a global contrast option (preferably where the day/night toggle is). The default night theme is too low contrast for me right now, coming from a brightness that is perfect for HN.
Maybe you want to scale all the UI elements? This has the same zooming effect as pressing Ctrl-+. Otherwise why not loop and set all the font sizes you want?
https://docs.rs/egui/latest/egui/style/struct.Visuals.html
I don't recall there being a high contrast option or slider, so your best bet might be trying to modify the values in this struct, or if that's not enough, then the values in the `widgets` field of it. You can customize every color in the UI.