To remove the new, ugly Bing sidebar on macOS, you need to create a local policy file. Note that doing this will disable the sidebar completely since Microsoft hasn’t yet separated the sidebar from the icon itself, though they say that’s coming. Anyway, here’s how to do it:
First, quit Edge is it’s already open and running.
Create the following folder on your Mac: LibraryManaged Preferences. Note that this folder is created in the root Library folder and not the one in your home directory.
Create the properly formatted .plist file on your desktop by opening Terminal.app and typing the following command:
/usr/bin/defaults write ~/Desktop/com.microsoft.Edge.plist HubsSidebarEnabled -bool false
This will create the file you need with the right option.
Next, move this file into the LibraryManaged Preferences folder.
Start Edge, and voila – the button is gone!
You can verify the policy loaded by going to edge:policy, and this should be the only one you see.
To disable this policy, quit Edge, move the file out of that folder (or set the value to true inside the file, using a text editor), and reboot the Mac.
Where there’s a will, there’s a way! 🙂