I can't find the "Leave Silently" option.
"Leave Silently" is available when you update KakaoTalk to v.10.2.0 or a higher version.

1. How to enable "Leave Silently" in Kakao Lab
• KakaoTalk> "Settings" icon (⚙️) on the top right corner of the More tab > Kakao Lab > Leave Silently ON/OFF

2. How to use "Leave Silently"
• Click the menu button in a group chatroom and tap the "Leave" icon.
• Check "Leave Silently" and tap Leave.

▣ Tips
• The More tab (...) is the 5th tab located at the bottom of the KakaoTalk screen.
• This feature cannot be used in private chats and Open Chat.
• The "Leave Silently" option will not be shown if you leave a chatroom using the swipe feature from a chat list or the chatroom editing feature.