Colif :
It applies to all of them, its just how win 10 works. Every folder is read only - have a look at any of their properties..
I have tried this before, when I first got win 10 last year. The folders are read only but it can be a permissions problem if you can't save to any of them.
??? Every folder?
This is a folder, on the root of C, created Dec 3, when I did a full reinstall of this OS.
A file copied into that folder today, if fully editable.
Once inside that folder, Right click, New....create a new text fiel.
I'm not seeing:
1. The issue the OP is having
2. The overall 'read only' ness of "Every folder is read only"