stopped working for the new version of slack

Stopped working for me today, on Windows 10. The message window is now positioned towards the top, and is obscuring all messages in chat, while pane is hidden, with F4. I tried looking at Inspect Element to reposition Message Input window, but couldn't figure out a fix.

Add-on was great and did exactly what I wanted, but it no longer works with the paid version of Slack (Slack Standard). (edit: this isn't working with any version of Slack apparently)

It works fine on one computer (Win 10), but on my other computer (Win 7, FF75.0), it hides the whole conversation window as well as the side pane.

Updated review:
Reinstalled to take a screenshot of what it looked like my first try, but this time around it looks great. It'll be much easier to participate in class with this, thank you.

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Previous review: I mean... it technically hides the sidebar. It messes everything else up though.

Thanx to the author!
But I still don't understand how the slackchat developers didn't think of it! :)