Pin, mute, favourite, clear and block

Two menus manage a chat: one for the whole chat (in its header), and one in the chat list.

The menu in an open chat

1. Open a chat and tap ⋮ at the top right.

   

The menu in the chat list

1. Press and hold a chat in the list.

   

Not tested: this guide shows these menus, but I did not try Clear Chat, Block Contact, Pin, Mute, Archive, Forward, Select, Add to task, Star or Pin on a message, so it does not describe what each one does afterwards.

There is also a Blocked Contacts entry under Settings; see Chat settings.