# If you'd like to omit non-matching lines from the result; add ';d' to the end of the expression.
sed -E 's/^(.*?)([\s:]+)?{([\s\S].*)?.$/$1,$3/gm;t' <<< "key:{value}
key:{valu{0}e}
key:{valu
{0}e}
key: {val-u{0}e}
key: {val__[!]
-u{0}{1}e}"
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