how migrate from office documents to modern web technologies based documents - advice welcome

[PackElend]

I hope that this the right place as this post covers different topic of web technologies but is mainly related to html.

Currently, all documentation is based on MS office. This makes it quite challenging if you want to integrate some functionality. Then you have either the option to go with VBA or VSTO. First is not that comfortable, second could be like taking a sledgehammer to crack a nut.

Simple things like simple controls, hiding text or basic maths can be easily realized by HTML.
So I would need an HTML text processor what focus on content (text) and allow me to add interactivity when I need it. That means switching to source code or showing additional panels only on request so that the author can focus on the textual content (A more programming familiar person would do the formatting/interactivity). In the long term, I want to have the ability to integrate things like SQLite and API calls. In addition, the output has to be in a single file otherwise it isn't portable in a practical way and users (who only fill in data) won't accept it.

I conduct some research and figured there isn't an all-in-one solution instead there are several options to meet some of my requirements. I wonder which is best to realize my long-term goals.

HTML5 offline app
It looks like that I either develop an offline HTML5 app what is well explained well, e.g. here:

1. Offline web applications: a working example
2. Tutorial: How to make an offline HTML5 web app, FT style
3. Creating HTML5 Offline Web Applications
4. How to Build an Offline Single-page Website
5. plus some background information on Single page apps in depth

markdown
The content could be generated in a markdown editor as recommended in What's a good, auto-saving, WYSIWYG HTML word processor? or just simple convert office documents to html5.

HTML editor / site designer
Alternatively, I could use an HTML editor or and visual site designer but the selection isn't exactly a small one for me to choose from. I found some help in:

6. Battle of the Text Editors: Atom, Sublime & Brackets
7. 26 Tools and Frameworks for HTML-based Desktop and Web App Interfaces
8. Free HTML Editors: The 16 Best for Web Developers on Windows
9. 14 Best Free HTML Editors
10. or even simpler for the standard office user: GrapesJS - Next generation tool for building templates without coding

single file website (app)
In my understanding there is still the problem that the output won't be a single file, will it?
I could make use of the archive formats but there aren't supported by all applications as well explained on What's the best “file format” for saving complete web pages (images, etc.) in a single archive?.
That could work if I do only simple things and integrated media object as Base64 encoded objects but it comes with the disadvantage of large overhead.

Desktop web apps
If I want to realize more complex things I would need to develop desktop apps using HTML/CSS/JavaScript but once again the selection is little as you can see in How to develop Desktop Apps using HTML/CSS/JavaScript? [closed].
I haven't found anything yet telling me if I can deploy a desktop web app as a single file.

A4 layout
The layout would be realized on the information given in How to make an HTML Page in A4 paper size page(s)?

office to HTML / html word processor

1. XSweet - The open .docx to HTML conversion tool
2. Wax / Wax II (web-based word processor)

HTML to office
For the transition phase, it would be nice to be able to transfer HTML to e.g. docx. Some options are mentioned in the references below:

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

So how shall I proceed?

Edited September 14, 2018 by PackElend