I store my Word documents in XML format to allow version handling. If I set the default file handler for the .xml file extension to Notepad++, Chrome, Excel, or any other program, then Windows attempts to open the XML file in the specified program. If I set the default app to Word, however, then the file opens in Notepad.
I made some small progress here by changing the registry key
HKEY_CLASSES_ROOT\.xml: now Windows opens a dialogue box asking "How do you want to open this file", with Word listed as the default.
I know this is a minor annoyance, but I'd really appreciate any suggestions..
As requested in the comments, here are links to screenshots showing that when I use the right-click menu to select the default file handler, Microsoft Word is selected, though I the associated tickbox is unchecked until I click it.