German and Finnish languages often require an “umlaut.” I don’t know how to use one in Libre Office.
This site is for questions and answers about LibreOffice usage. You question relates to the operating system and thus is off-topic here. Besides, it is not a good question as you do not specify your operating system, so, get a downvote, read these guidelines and learn to ask good questions. Refer to your operating system manual on setting up input methods.
Have you tried searching to see if anyone case considered this question before? For example the query "How do I type a simple umlaut in Libre Office? " could be relevant. äü äü
Of course the answer varies slightly depending on your computer setup.
C4 followed by
ALT+C in some locales)
E4 followed by
Ö: type `D6` followed by `ALT+X` ö: type `F6` followed by `ALT+X`
Ü: type `DC` followed by `ALT+X` ü: type `FC` followed by `ALT+X`
if you don’t want to install additional keyboard layouts on your operating system and you don’t want to switch keyboard layout and text language while editing German text (which would be the way to go, if you are working multi-lingual texts).
Insert > Special Character…
gives you a point-and-click menu of characters.
At the top right, you can select a “subset”; the ones you may be interested in are
- Latin-1 (examples: ä,ö,ü,ß,ø)
- Latin Extended-A (example: ł,œ)
I do not know the Northern European languages well enough to tell you about Finnish characters, but they should be in there somewhere.
(Availability of characters beyond Latin-1 may depend on whether you have fonts installed with Unicode support)