How to Hide Channels
You can hide the channels that you have no unread content in, by clicking the category name. If a new message is sent in that channel, the channel will re-appear but if you mute the channel it will remain hidden. You can unhide the channel by clicking the category name again.
If the arrow next to the category name shows upside “^” it means the channels are not hidden. If it shows the right side “>” it means channels are hidden.