I answer my question because it is always very difficult for me to find the reference to this solution:
# rubocop:disable Metrics/MethodLength
def my_code
..
end
# rubocop:enable Metrics/MethodLength
Same for multiple cops:
# rubocop:disable Metrics/AbcSize, Metrics/MethodLength
def my_code
..
end
# rubocop:enable Metrics/AbcSize, Metrics/MethodLength
Documentation: https://docs.rubocop.org/rubocop/configuration.html#disabling-cops-within-source-code