I never used Hypercard back in the day. But I recently started using Obsidian, and it has the idea of cards/notes and linking to them. It’s built on Markdown files, and you can use it for Zettelkasten if you wish.
Linking notes (or even creating them) is as easy as type [[ and then type the (new) name and ]] and boom it is linked or a new note created (as you type the name it searches for existing notes of course).
A powerful idea, but it appears that it is anything but new lol
Use for free on Mac, Windows, Linux. Support them for early access to iOS and Android beta apps. Stores all your notes as plaintext markdown files.
Optionally pay to sync (encrypted) with their sync across devices.
I really like Markdown - that’s what brought it to my attention.