Allow the user to automatically type the login information. First the user opens the proton pass extension or more likely desktop application.
Upon clicking on an specific login field, the user can press a keyboard shortcut, such as Ctrl+V which will fill the last select form field and fill it with the selected login information.

The procedure to fill the information in could be solved by programmatically minimize the Proton Pass application and automatically typing in the copied login credentials.

The entering of credentials could even be neatly animated with a 50ms delay per character to present the illusion of characters being typed in.

This feature would be a great incentive to upgrade to pass pro.