Like in other messenger apps, you can hide chats that you no longer want to see in your general list of chats anymore. The chats can then be found in a separate section with all other hidden chats and will only appear outside of hiding if you want them to. So even if messages are sent within the hidden chat they will not bother you.
To hide a chat, hover your mouse over the chat within the menu and click the "..."-Symbol that should appear then. Select "Hide"
As soon as you have clicked "Hide", you will have to confirm your choice. Afterwards, the chat will no longer be visible with your other chats. In addition to that you won't be receiving any notifications regarding hidden chats. To access hidden chats simply click "Hidden" at the very top of the chat menu.
This will lead you to a collection of all hidden chats. New messages that are being sent into hidden chats will not cause the chat to reappear. To Make a chat reappear, open your hidden chats and click the "..." symbol next to the desired chat again.
Choose "Show" and the chat will automatically reappear and unmute itself.