# 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]*?^[^][]*=)\[\[[^][]*\[[^][]*\]\]\K\]\R[^][]*\[(.*)\]$(?!\R\1)/, \2]/gm;t' <<< "1 NameA - DirectionA=[[StreetA @ StreetB,[Lat,Long]]]
1 NameA - DirectionA=[[StreetC @ StreetD,[Lat,Long]], [StreetF @ StreetE,[Lat,Long]]]
1 NameA - DirectionB=[[StreetE @ StreetF,[Lat,Long]], [StreetG @ StreetH,[Lat,Long]]]
2 NameB - DirectionC=[[StreetI @ StreetJ,[Lat,Long]], [StreetK @ StreetL,[Lat,Long]]]
2 NameB - DirectionD=[[StreetM @ StreetN,[Lat,Long]], [StreetO @ StreetP,[Lat,Long]]]"
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