The sidebar that shows your teams and chats in Microsoft Teams can be hidden when you don't need it. Microsoft has made changing these settings very unintuitive, but it's easy once you know where it hides.
Having a sidebar or navigation panel on the left side of an app is super normal (almost all email clients have one, as an example) and many apps give you the option to turn it on or off. Microsoft Teams is no exception, But for some reason, the company made the change hard to find and you can't toggle the sidebar on and off if you have a chat open.
Simply, this means that you can turn the sidebar on and off when you have an open tab in a channel, as long as it is not the channel “Publications”. You cannot turn the sidebar on and off if you are in a chat.
To toggle 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. To show it again, click the diagonal arrows again.
One clue to Microsoft's thinking is that if you hover over the diagonal arrows, the tooltip says “Expand tab” if the sidebar is visible, O “Collapse tab” if the sidebar is not visible. Clearly, the design team was thinking more about giving extra screen real estate for the tab you're looking at, instead of letting you hide the toolbar just because you don't want to see it.
