I like the new 1Password Mini so far, but I've encountered some pages where it just doesn't pop up when pressing the shortcut.
As far as I can tell, it affects pages where only one pair of username/password is stored but no login mask has been found (e.g. this very discussions.agilebits.com). It seems that 1Password tries to fill in credentials but does not find anything to fill them into.
What I've also found while typing this post is that in this "Ask a question" form, 1Password will override the "Title" field with my username when I press the Mini shortcut — however I can't say whether that's a regression or if it has always been that way.
Just my 2 cents, keep on the great work!
1Password Version: 7.3.BETA-2
Extension Version: 22.214.171.124
OS Version: macOS 10.14.4
Sync Type: Not Provided