It is perhaps a dirty hack, but I redefine the "editor" string in biblatex manually with \DefineBibliographyStrings{nynorsk}{editor = {(styr\adddot)}}, which will give me both the Norwegian word for "editor" and a parenthesis around the word.
With the parenthesis, though, I feel there's no need for the comma following the editor name. The same question has been asked before, but the accepted solution doesn't change anything for me (see the MWE below).
My question is, how can I remove the comma after the editor name?
\documentclass{article}
\usepackage[style = authoryear-comp, sorting = nyt, language = nynorsk, sortlocale = nn_NO, backend = biber]{biblatex}
\usepackage{xpatch}
\xpatchbibmacro{date+extradate}{\printtext[parens]}{\setunit*{\addperiod\space}\printtext}{}{} % remove parenthesis around year in bibliography
\xpatchbibmacro{bbx:editor}{\addcomma\space}{\addspace}{}{} % <- this doesn't change anything
\DefineBibliographyStrings{nynorsk}{editor = {(styr\adddot)}}
\usepackage{filecontents}
\begin{filecontents*}{\jobname.bib}
@BOOK{ordbogoverdetdanskesprog,
TITLE = "Ordbog over det danske sprog",
YEAR = "1919--56",
EDITOR = "H. Juul-Jensen",
LOCATION = "K{\o}benhavn",
PUBLISHER = "Gyldendal"}
\end{filecontents*}
\addbibresource{\jobname.bib}
\begin{document}
\nocite{*}
\printbibliography
\end{document}

