I’m unfortunately still not seeing any options in context menu > Dictionaries, having tried both Dutch as well as German dictionaries. Contrary to the screenshot in the beta announcement, I’m not even seeing en_US in this list although spell-checking English text does work.
Just to be sure I made no mistake with installation: is it enough to copy nl_NL.aff and nl_NL.dic to C:Program FilesEmEditorDictionaries or are additional steps required?