I am looking for an HTML editor that live interprets the HTML in the same buffer as the one I'm writing in. Meaning that it would look similar to the following, as a simple example:
All the solutions I've found so far provide a separate view for the rendering, which is great for websites but worse for a general markup language. I wouldn't mind there being a limited set of usable tags, either, if that enables this functionality.
A good example is Overleaf's Rich Text mode, which implements such a thing for a subset of LaTeX.
I'm fairly flexible concerning OS or Web-app; my price limit would be around 50€. I'm also interested in the pure feasibility as well, so even pricier solutions would definitely interest me.