Sorry, I know this question is far out of scope with anything Decker-related. However, I am currently building a little Terminal UI app, using Python, and was wondering if anything in the spirit of Decker exists for Terminal UIs?

Could you elaborate upon what you mean by "Decker-like"?

Lilt is a command-line interpreter for Lil, and it is like Decker in the sense that it's Decker's scripting language, it's highly portable, and it has a small API of useful bits and pieces that fits comfortably inside your head at once.

Do you instead mean something more visual and drag-and-drop, from the perspective of editing CLI apps, using them, or both?

I am currently building a visual app for note taking and browsing.

This works  on a hierarchy of note files, supported by an SQlite database for searching and arbitrary relationships. I use it on a small (5'', 320x240) display, connected to a Raspberry Pi 400,  cyberdeck-style. The UI, implemented  with PicoTUI, runs in a terminal window and can be operated by keyboard alone.

Decker-alike in this setup could mean that note files would be individual slides or whole decks of slides. A render engine would display a slide full screen in a terminal window,  using  only ANSI  terminal characters  for  both widgets and even low-res images. Decker & Lil would provide widgets and scripting, similar what TurboVision & TurboPascal did back in the 90th.