Android #

Unread #
  1. Go to the chat list.
  2. Tap and hold on a chat.
  3. Tap to select any other chats.
  4. Tap Menu at the top.
  5. Select Mark as unread.
Read #
  1. Go to the chat list.
  2. Tap and hold on a chat.
  3. Tap Menu at the top.
  4. Select Mark as read.

iOS #

Unread #
  1. Open CoolApp to view your chat list.
  2. Tap and hold on the chat and swipe to the right.
  3. Tap Unread.
Read #
  1. Open CoolApp to view your chat list.
  2. Tap and hold on the chat and swipe to the right.
  3. Tap Read.

Desktop #

Unread #

Select the chat > Chat Settings  > Mark as unread

Read #
  1. Leave the chat.
  2. Select the chat.