Maybe I've overlooked but it seems the Microsoft Edge Plugin is not listed on:
[Get 1Password for your browser]
[Download Browser Extension] Button
Not using Chrome?
[Show all extensions] --- Link only shows Safari, Firefox & Opera ?
I now have Edge 1Password extension (though not auto filling at the moment), but after some digging about I realised it was in the Microsoft Store.
Perhaps make it more obvious to those who have not been keeping up with machinations of Microsoft and extensions for Edge.
1Password Version: 6.8.496
Extension Version: 126.96.36.199
OS Version: Windows 10 Pro Version 1709 OS Build 16299.192
Sync Type: 1Password membership