By default, 1Password searches for text in the major fields only, and this can be changed with a button "Expand Search to All Fields" which shows up when a certain search term generates no results.
Alternatively, this setting can be changed in the 1Password mini's gear icon as shown below.
However, there doesn't seem to be a place where users could change this in the main app. I went through every tab in the preference page and the entire toolbar but couldn't find it anywhere.
This means that for someone who doesn't know about the aforementioned 1Password Mini option, they will be unable to go back to "Search Major Fields" after changing to "Search All Fields."
I believe this is an UI oversight, please correct me if I'm wrong. Thank you 1Password team.
1Password Version: 7.2.5
Extension Version: Not Provided
OS Version: 10.12.6
Sync Type: iCloud