How to set proofing language regardless the keyboard layout on Windows?

On my Windows 10 I am using 3 different keyboard layouts. Whenever I type something in some application the operating system is matching the proofing language for spelling and grammar check with the language of the keyboard layout in use: for example, when I am using the ENG keyboard layout then English is used as proofing language.

It's often the case though that I am using the keyboard layout of my physical keyboard, even when I am writing in a language different from the one of the keyboard.

How do I tell the operating system, to use a specific language for proofing, regardless the keyboard layout?

1. Go to settings > Region & Language.
2. In "Languages" > Add a language.
3. Add the language that you want to use for language proofing.
4. Click on that new added language and hit "options".
5. Add the keyboard layout that you want.
6. Switch proofing languages with AltShift.