Created attachment 148059 [details]
1. Open a Writer document in localized LibreOffice Online, e.g. in German version.
2. Open Format -> Bullets and Numbering from menu, and select the Customize tab. (In German: Format -> Aufzählungszeichen und Nummerierung, Anpassen)
3. The character styles dropdown is in English as it is shown on the screenshot.
The relevant piece of code could be in here:
Moving to NEW and turning it into an easyhack since there's a codepointer
this is a specific symptom of a broader problem: the localized built-in style names are stored in the model of all applications (at least sw and sc, pretty sure also sd), instead of the model storing only the en-US built-in style names and the UI creating the translations.
there is bug 123397 for an ODF interop issue with the same cause; the solution proposed there doesn't look like an easy-hack.