I want to perform autotuning via communication on a UT with CC-Link communication. Should I turn AT_L1 which is assigned to the OUT area in the profile to ON (=write 1)?

Autotuning is performed when you turn AT_L1 in the OUT area to ON (= set to 1). Please make sure that AT_L1 in the OUT area turns OFF (= set to 0) after autotuning is finished.