# 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*\b(\d+(?:[.\/]\d+)+)\b.*?-.*?\b(\S+)\b\s*(\d+)\s*$/$2 $1-$3/gm;t' <<< "GPX 10.802.123/3843 1 - IDENTIFIER 48"
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