Font sizes and families are also a relatively little-used way to visually distinguish things in a code editor.

Years ago I used to work on C++ code in a commercial editor called Source Insight [1]. At its default settings, it would do things like:

1. Show function and class names in HUGE fonts in declarations and definitions, so you always knew what was a declaration as opposed to a use

2. Show nested parentheses with the outermost parens being biggest and getting smaller as you got further in

3. Show comments in a proportional sans-serif font instead of a monospaced one so that you could tell where the comments were even if you have color blindness

Those features, along with having a C++ parser and code relationship visualizer much faster than the Visual Studio of the day without having to parse ahead of time (a la ctags), made Source Insight a near standard in my company. I still miss it on occasion.

[1] https://www.sourceinsight.com/feature-details/