How to Set Default Apps on Windows 10 with a script?

For each of the filetypes that you want to set a default app for, find the filetype it is associated with.

For XML, at a CMD prompt execute this:

Assoc .xml

https://docs.microsoft.com/en-us/windows-server/administration/windows-commands/assoc

That will tell you the filetype is "xmlfile"

To set the default app for an "xmlfile", you'll use Ftype:

Ftype xmlfile=C:\Program Files (x86)\Notepad++\notepad++.exe %1

https://docs.microsoft.com/en-us/windows-server/administration/windows-commands/ftype

Once you know the filetype for each of your extensions, add a line for each of them to your batch file.