Umlaut characters using UK keyboard on Windows (no NumPad)
You can use the United Kingdom Extended keyboard instead of the US International.
Using UK Extended, to insert an umlaut character, hit AltGr+2 then the character (eg. u to ü).
Microsoft Docs has a keyboard simulator to show what key combinations will give you the various diacritics in UKX.
note: AltGr is the Alt key to the right of the space bar.