How to manually associate a file type with a program?

Question

Windows

Unable to associate file type with program. There is no result through the control parameters. It doesn't work in the file properties either. It costs Windows 10.
What and where should be written in the registry so that such types as css, php, etc. are associated with the editor, and not with a notepad or "select application"?

Answer 1

Manual solution - Win + R > regedt32 (or regedit) > Ok > The very first branch - HKEY_CLASSES_ROOTand there is a database of associations > select any familiar "editable" file, see how everything works there > export > edit to suit your tasks > add to the registry

Answer 2

Start - "Default Application Settings" (in the search) and the button from the screenshot