Tools like Vivado and Quartus are proof that a GUI isn't necessarily better.

What do you mean niche market?

I would find something like marktext except for Typst amazing. This would enable one to have a document on the left side of your screen and a Typst document on the right, so you don't have to have two Monitors for taking notes while reading for example, as you currently need to have with Typst, because it's YAFIYGI and there's currently no WYSIWYG Typst editor afaik

There is nothing stopping 3rd party projects from doing this. In fact just such apps already exist. See for example typstudio. Also you don't have to have two monitors to have an editor window and PDF viewer open side by side. If you leave the compiler running in the background watching for file changes and use a PDF viewer that automatically updates the experience is pretty good and you get to use your favorite editor.

Some editors also have preview plugins available that render in a side by side pane already too.

Sorry, I meant a different pdf that I read on one side of the monitor and then can take notes on the other side of the monitor. That's only possible with a WYSIWYG editor, which typstudio isn't, right?

Yeah, I use LyX in a similar way, but the experience could really be much better.
There also was Scientific Workplace, I wonder how much sales they had - not too much probably as they are out of business.
I also tried Mathematica some time ago, but there have been other quirks, maybe I'll try again

The issue is Lyx is you gain a much better way to fix errors (something that is less of an issue with typst as you can see changes as soon as you do them) but you end up with limitations when typing math (sometimes it's actually more flexible to type things than using it the gui, when you know the command but not the way to do it with the gui or when the gui way is actually impeding writing), and there are other weird things as far as the UX goes in lyx (having a separate type of file and sometimes weird looking tex files). Basically you get a GUI-like experience but you loose any way to tweak the tex code.

I do think some gui can be useful but you have to be careful with design. You could do a word-like interface for typst (for text editing and images, but to edit equations I don't see how you could do it without showing the related code) but I can't see it any other way than a separate preview mode. I feel it would be a much better UX to have it as an option, with the other workflow accessible as well at the same time. I don't think all of the things you can do with typst (the actual program-oriented things) can translate to a GUI interface or if this would even be desirable.

Tried typstudio a few weeks ago and couldn't get it to work directly out of the box. I don't blame the developers as the project is, as stated by them, a work in progress (WIP).

Currently am using VSCode with two extensions for Typst – Typst Preview and Typst LSP.

I am happy to share that this set-up:

1. Has "live compilation". Results of edits are shown in real-time in a separate VSCode tab that shares screen real estate with the tab showing the typ file I'm editing. (Thanks to Typst Preview)

2. Is able to let me jump to content in pdf file being previewed (see point 1) when the associated content is clicked in the tab showing the typ file. This jump also goes the "other way" – by clicking on content in the pdf preview, the tab showing the typ file scrolls to the related part. (Thanks to Typst Preview)

3. Automatically saves the resulting pdf file whenever the typ file being edited is saved. (Thanks to Typst LSP)

Problems:

Happy to report no major issues, and am pretty satisfied with the smoothness of this set-up thus far. ⛵️🌊🌊

One minor issue that occurs from time to time, and especially after sleeping the machine or leaving the machine idle, is the need to "re-engage" Typst Preview due to it having stopped watching the typ files that it's supposed to be watching. Luckily, resolving this is straightforward and quick. Ctrl + shift + P in VSCode to pop up the "omnibar" (sorry "omnibar" is likely not standard VSCode terminology), typing "preview" to surface the command "Typst Preview: Preview Current File", and finally pressing enter to execute it.

In an ideal UX case you would be able to write in markup AND edit in the output view

This is exactly what would be needed. Typst is very nice like it is intended now, and completely fine for people with computational backgrounds. However, at least in academia, one often has to collaborate with non-computational people, and many of them will be overwhelmed by the syntactical complexity of WYSIWYM. For those cases, it would be invaluable for them to be able to edit and comment on the right hand side, in the preview panel. Importantly, this does not require them to be able to edit everything. For example the math can be left read-only. If they can edit the text parts and also extend them, that would be enough. People who are capable to understand and edit the math will also have no issues to master the typst syntax.

Like the swiftlatex editor, but without aparently discontinued development and in modern.

It would be very convenient to have the ability to click on a part of a rendered mathematical formula and have the editor's caret be transported to the Typst code responsible for it. For a start, even slightly inaccurately transporting the caret to the vicinity of the Typst code would be helpful.

That already exists in the web app, and I think in Typst LSP as well.

Perhaps a counterpart to a more robust version of https://cortexjs.io/mathlive/ could be a solution.

I second what @felidz suggest : mathlive is a good exemple of the use of a gui to edit complex math equations.

I actually like TeXmacs style editting more, although it is built on a technology that I don't like. TeXmacs has convenient shortcuts for common math symbols. LyX is also a good alternative.

I am a LyX user, too. I believe many who prefer markdown+script over GUI might have less experience of typing heavy mathematical formulas.

yeah, that's basically what I was after.
For basic stuff markdown is obviously fine. For utmost generality a scripting language is great.

For devs with a CS background (how likely is that?) all they probably care about is having code inside of the main text, which is trivial with markdown.

But all approaches struggle with editing math and tables. Not to mention math inside a table ;-)
The existence of "equation editors" is a farce pointing at this issue from the other direction.

All WE want is to write text WITH math! In a convenient way.

There are plenty of Markdown editors that are not "code editors" and support CtrlI for Italic for example. Some hide the formatting marks, others show them but give you shortcuts for creating them. There are even plenty of them geared specifically at writers not coders.

Obviously not many of those exist yet for Typst (although conversion via pandoc is of course an option), I'm mostly just pointing out the category error and that there is a whole world of editors in between "code editors" and WYSIWYG, and as a prose author I would suggest the best way to not get lost in either the code or the exact output formatting while writing is somewhere in-between.

I've tried a few markdown editors before that are a bit more wysiwyg-ish. But they all kinda sucked. To be fair though, it's been a few years so maybe I should revisit the topic.

Currently I'm writing in LibreOffice, which is... fine. It's very slow on my wayland laptop. But I also just noticed that trying to combine different documents (one for each scene) with pandoc strips all my in-line formatting (i.e. done the way I described in my OP, instead of setting a paragraph style).

That + .odt files being very annoying to keep versioned (and .fodt files being such a fire hose of diff for every save) made me curious to use typst as a storage format, which I can then generate .odt files (to send to my editor) and whatever else from when the time comes.

Anyway, I know writing UIs is a lot of work (too much work). I wanted to weigh in my opinion/ situation in case anyone with the know-how desires to feel nerd sniped