How to migrate from office documents to documents based on modern web technologies

Currently, all documentation is based in the MS office. This makes it quite challenging if you want to integrate some functionality. Then you have the option to go with VBA or VSTO. First it is not so comfortable, second it could be like taking a hammer to break a nut.
Simple things like simple controls, hiding text or basic maths can be done easily using HTML.

So I would need an HTML text processor that focuses on the content (text) and allows me to add interactivity when I need it. That means changing the source code or displaying additional panels only on request so that the author can focus on the textual content (a person more familiar in programming would do the formatting / interactivity).
In the long term, I want to be able to integrate things like SQLite and API calls.
In addition, the output must be in a single file; otherwise, it is not portable in a practical way and users (who only complete the data) do not accept it.
I do some research and I thought that there is not an all in one solution, but there are several options to satisfy some of my requirements.
I wonder what is the best way to achieve my long-term goals.

HTML5 offline application
It seems that, or, I develop an HTML5 application without connection, which is well explained, for example. here:

  1. Offline web applications: a working example
  2. Tutorial: How to make an HTML5 web application offline, FT style
  3. Creating HTML5 web applications offline
  4. How to build a website without a single page connection
  5. more detailed information on one-page applications in depth.

The content could be generated in an error reduction editor as recommended in What is a good WYSIWYG HTML word processor with automatic saving? or simply convert Office documents to html5.

HTML editor / site designer
Alternatively, you could use an HTML editor or a visual site designer.
but the selection is not exactly a small one so that I can choose.
I have found help in:

1. Battle of text editors: Atom, Sublime and square brackets
2. 26 Tools and frameworks for HTML-based desktop and web application interfaces
3. Free HTML editors: the best 16 for web developers in Windows
4. or even simpler for the standard office user: GrapesJS – Next generation tool to create templates without coding

single file website (application)
In my opinion, there is still the problem that the output will not be a single file, right?
It could make use of the file formats, but it is not compatible with all applications, as explained in What is the best "file format" to save complete web pages (images, etc.) in a single file?
That could work if I just do simple things and integrated multimedia objects like objects encoded in Base64, but it has the disadvantage of a large overhead.

Desktop web applications
If I wanted to realize more complex things, I would need to develop desktop applications with HTML / CSS / JavaScript, but once again, the selection is minimal, as can be seen in How to develop desktop applications with HTML / CSS / JavaScript? .
I still have not found anything that tells me if I can implement a desktop web application as a single file.

A4 design
The design would be done in the information provided in How to make an HTML page on A4 paper size pages?

HTML to the office
For the transition phase, it would be nice to be able to transfer HTML to, for example. docx Some options are mentioned in the following references:

  1. How to convert an HTML file to Word?
  2. Convert html to docx using pandoc
  3. html-docx-js
  4. Convert HTML to Docx in c #

So, how should I proceed?

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