Navigate Around Chats
The left-hand sidebar displays all your contacts — channels, feeds, people — arranging them by recent activity.
Use tabs on top of the sidebar to filter the contact list and show only contacts of a particular type:
For example, choose DMs to only display your direct message contacts:
Customize your contact list for easier navigation
In the default arrangement, the Home tab lists all your channels and conversations. To reduce the clutter, you can customize the Home tab to only display new (unread) messages, or hide some categories (e.g. Issues, Automation) altogether. Hidden contacts/messages can be always found under their designated tabs.
Click 
to open the settings:
You can also remove unwanted tabs from the top of the list using these toggles:
Channels and conversations from the removed tabs will be shown in the Home tab.
Contact list appearance
To further reduce the clutter, you can change the way your channels and conversations appear on the contact list.
Click and go to the Channel List tab:
You can:
Choose to display favorite or all contacts as a single line entry.
Hide closed review/merge request conversations as well as resolved issues.