How do I archive chats?
Chats can only be archived in Threema for Android at the moment.
In the chat overview, swipe from right to left on a chat to archive it. 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 “X archived chats” button.
In order to move an archived chat from the archive back to the chat overview, tap and hold the chat until the action icons appear in the title bar. There, tap the icon next to the trash-bin icon.