After clicking on the “Expand content” command button I have found myself scratching my head:

• Where is the “Collapse content” command button?
• Where has the command ribbon gone?

Well, the command ribbon is still there, it is just hidden by the ‘top placeholder’. Or more precisely, what has loaded into the ‘top placeholder’. For example: Hub Site Navigation or a SPFx Extension.

Having done a few web searches, I’m not the only one seeing this bug and apparently Microsoft is planning to fix the bug. In the meantime, here are two workarounds:

1. Delete your browser cache (including cookies) and reload the page
2. Open your browser’s developer tools (e.g. press F12).
   • Select the ‘Console’ tab
   • Paste in the following code
   • Press enter

document.querySelectorAll("button[title='Collapse content']")[0].click();

And now you should see the modern command ribbon again.