In the Spell Check menu item, you can create a dictionary for spell checking.
All the words included in the dictionary are no longer flagged as misspelled. By using the "Insert" / "Delete" buttons from the "Spell check" ribbon and editing the single entries, the list can be expanded and corrected. The list can also be added directly in the context menu in the application (see "Text functions" / “Spell check").
List of all own dictionary entries
Spell check for non-German language registration
To ensure that the spelling check also works when logging on in an alternative language, it is necessary to install the corresponding language packs in Windows.