Slack sidebar automatically collapses: how to keep it permanently open?

Apparently I hit some shortcut combination that caused Slack to automatically collapse the sidebar that contains the list of Channels and Direct Messages. There is an option to **temporarily** show the Sidebar in the View menu: we now temporarily see the left sidebar But after clicking in conversation area the sidebar will still hide itself again. I have looked at Preferences | Sidebar and it does not have any setting related to hide/show: Is there any way to do a "factory reset" on the Slack settings but retain the existing channels? In other words I do not want to completely reinstall Slack unless necessary.