It's also not in the main firefox browser windows either (right-click 1P context menu). But at least I have the icon in the toolbar to fill in passwords in the main browser tabs.
I could not customize the toolbar in the firefox popup window.
I tried to go to the firefox 'addons' window and see if additional settings can be set there for 1P extension. No luck there. (no settings option).
So with no right-click context, how was I supposed to fill in the password without access to the icon for that tab/window?
Google chrome has the right-click menu option (44.0.2403.155 m (64-bit)):
1Password Version: 126.96.36.1995 (12)
Extension Version: 4.4.2
OS Version: 6.1.7601 SP 1 (win7 x64)
Sync Type: dropbox