The sidebar with your teams and chats in Microsoft Teams can be hidden when you don’t need it. Microsoft has made changing this setting very unintuitive, but it’s easy once you know where it’s hiding.
Having a sidebar or navigation pane on the left side of an app is completely normal ̵
This basically means that you can toggle the sidebar on and off if you have a tab open in a channel, as long as it is not the “Posts” channel. You cannot toggle the sidebar on and off when you are in a chat.
To switch the sidebar, open a tab in a Teams channel and click the two diagonal arrows to the right of the tabs.
This will hide the sidebar. Click the diagonal arrows again to display it again.
A clue to Microsoft’s thinking is that if you hover the mouse pointer over the diagonal arrows, the tooltip reads “Expand Tab” if the sidebar is visible, or “Collapse Tab” if the sidebar is not visible. Obviously, the design team thought more about giving extra screen real estate for the tab you’re looking at, rather than letting you hide the toolbar just because you don’t want to see it.