Submitted answers for writing plaintext / code / IDE.

So yes, the built-in Notepad can be used to take notes.
You may have created a good note-taking environment when you divide the topics into different folders.

But people don't take notes that way. And this is not a portable method.

You are reading an article on any website. You want to save the article somewhere. Perhaps there are sentences to underline.
Nothing on the web is likely to stay the way you first found it. Some contents die. And those contents can be very important.

This is why people use applications such as OneNote and Evernote.

You can tag notes in those applications, you can save websites content , and you can connect between notes...

These features are not what notepad supports.

And most of these apps also have a mobile app.
This way, people can take new notes, update, delete, etc., even while on the go.

If you know of such an application, please let me know.
If there is still no note-taking application available, I'll write it in Golang.
I can not believe this. Maybe I've tested 10 apps and none of them are compatible with screen readers. We are in the 21st century. It's so scary.