# If you'd like to omit non-matching lines from the result; add ';d' to the end of the expression.
sed -E 's/(?:\G(?!^)|^genre:\h*").*?\K",\h*"/, /gmi;t' <<< "genre: \"drama\", \"thriller\", \"mystery\", \"espionage\"
genre: \"drama\", \"sci-fi\"
NOT genre: \"drama\", \"sci-fi\""
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for SED, please visit: https://www.gnu.org/software/sed/manual/html_node/The-_0022s_0022-Command.html