How to type"diéresis" - I have just found accidentally.
How to type "umlaut" - I have just found accidentally.
If you have Spanish or US International keyboard you press accent key followed by letter to get accented letter, like this - ó, ú, é, etc...
If you press shift+accent key followed by letter you get umlaut - ö, ü, ë, etc...
Hope it will be of help for someone
Yea I figured that out today too. Very useful. Also check this image out. This is the International Spanish keyboard. If you look at the control panel down the bottom you can see how to produce each quadrant of each key. The fourth quadrant however is usually Ctr+Alt (eg Ctr+Alt+2 makes a @).