# If you'd like to omit non-matching lines from the result; add ';d' to the end of the expression.
sed -E 's/(?=\b\d+\))/\n/g;t' <<< "1) test 1 22) test 2 333) test 3 4444) test 4 55555) test 5"
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