How do I archive chats?

In the chat overview, swipe from right to left on a chat to archive it (on iOS devices, you additionally have to tap on the gray button with the box icon). The chat will be removed from the chat overview, but not deleted. 

To access your archived chats, scroll to the end of the chat overview, and tap the button “X archived chats” (Android) or “Archived Chats” (iOS).

In order to move an archived chat from the archive back to the chat overview, proceed as follows:

• Android: Tap and hold the chat until the action icons appear in the title bar. There, tap the icon next to the trash-bin icon.
• iOS: Swipe left on a chat and tap on the gray button with the box icon.