You can set up notifications individually for each Topic and group chat that you are participating.
<PC / Web>
Go to the upper right corner in your chat room and select the ring icon to turn off notifications. Click it again to turn it back on.
<Mobile>
Select the menu [...] icon on the upper right corner of the Topic, and the Topic Info screen will show.
In Topic Info, go to notification menu to turn off or on notifications for the Topic.
Please keep in mind that you will still receive notifications for @ mentions.