Let me just use this promise hand to send you a pic.

Obsidian is a way you could do this sort of thing. Uses markdown language to generate new pages and articles. Comparable to a much lighter weight OneNote with extensibility. Introduced by a GenX to me to my pleasant surprise.

Personally free, not open source, can be integrated into git easily. Probably some legwork to transition your existing notes in but likely a improvement over notepad++. Besides the executable the storage of notes is all plaintext with markdown language.