svg-tag-mode VS auto-complete

That is a module that let's you replace occurances of regexes with svgs (https://github.com/rougier/svg-tag-mode)

https://github.com/rougier/svg-tag-mode is one ingredient, which makes org documents look more fancy.

You're looking for svg-tag-mode. It's on ELPA and MELPA, so you should be able to just use-package one of those (don't forget to package-refresh-contents).

tag looks like from https://github.com/rougier/svg-tag-mode/tree/07640c97a1dcc305010a384fffdaa7788c342da7

I agree, that's a really great example. It would be even more natural for tags in org-mode, which already supports drawing tags away from the text itself to a far-right column, but they really could be moved in the other direction to the left of a hairline next to the bullets, and they'd be more readable.

BTW, Nicolas has a lot of interesting packages exploring use of graphical design elements in Emacs apart from the Nano Emacs stuff; for example, there's https://github.com/rougier/svg-tag-mode. I love how he chooses to represent dates and dates with times attached, and to distinguish active vs. inactive dates with shading rather than "[" and "<". That actually makes it easier to spot a common org-mode mistake without having to call up the agenda.

It's here: https://github.com/rougier/svg-tag-mode/blob/main/examples/example-2.el (just evaluate the whole buffer)

Specifically this is the one: https://github.com/rougier/svg-tag-mode

lsp (and corfu which I have not used yet) might be the way to go forward. I'll try again next year. Autocomplete on the other hand seems to be looking for a new maintainer.