I have been using Notepad2 on Windows XP for a long time now.

I used Komodo Edit for ever but can't get it to run or compile on Apple silicon or some tries at VM. Found Geany on Raspberry Pi and also on Homebrew for macOS. Geany is awesome. The sidebar symbol tab that navigates code by clicking sub names is paradise. The "Overview" plugin adds adds that extra dimension to navigation. Geany wants to be configured for maximum effect:

Edit > Settings
View > Change Color Scheme
Tools > Plugin Manager

Some fun plugins:
Addons
Export
File Browser
HTML Characters
Line Operations
Lipsum
Mini Script
Overview
Save Actions
Split Window
Tableconvert
TreeBrowser

Kudos on attempting to write your own editor with real time syntax highlighting! What I miss about Komodo is the real time bug detection for Perl, that was crazy. But it still runs on Intel...