If you do not often access a folder, you can remove the folder from favorites. Please follow the steps below for details (or see how to add folders to favorites):
Step 1: In the Outlook message window, click the "Home" tab;
Step 2: Move mouse to the folder (e.g., Inbox) and right click to show the dialog box, click the "Remove from Favorites";
Step 3: The "Inbox" folder is removed from Favorites.