There is nothing particularly wrong with the M$ Notepad but the open source Notepad++ is so much better.
I could not work out how to associate the Notepad++ with .txt files as it never appeared on the Apps list in Default programs in settings. The program appeared in the menu when you right clicked on a file so it was possible to load a text file into it that way but Iwanted to just double click on a text file and have it load into Notepad++ rather than M$ Notepad.
Anyway here is how to do it:
Run Notepad++ as administrator. <<< this is the key
Go to Settings > Preferences > File Association.
Select Notepad “.txt” in Supported Extensions panel.
Click the "-> " to move it to Registered Extensions panel.
Click Close then go to Windows Default Apps and try to Associate .txt there
Easy when you know how.
If you edit or create text files, batch files, Java, VBA etc then Notepad++ makes your life so much easier with many useful facilities including spellcheck, tabs and so much more. Try it.
If you only want to take notes and you have Google and Android phone then Google Keep is great. I use it for shopping needs. I have tablet in the kitchen, add what I need to a list and it is synced accross to my phone.
I don’t disagree with you about Keep as a notetaker or shopping list (my main use for it) but Notepad++ is a text file editor specifically for a computer, free and open source.
Being a text editor means that there is no formatting applied but editing a plain text file is much easier using Notepad++ rather than Notepad or a word processor
It also has specific applications, for example it colours keywords and variables in batch files which make them much clearer and easier to edit but this has no effect on the output. It recognises specific files from their extension (.txt or .bat).