# If you'd like to omit non-matching lines from the result; add ';d' to the end of the expression.
sed -E 's/(?:\baccord\b|\G(?<!^))[^)\s]*\K\s+/%20/gm;t' <<< "A scripture reference like [Luke 2:12, 16](accord://read/?Luke 2:12, 16) should be clickable."
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