Proton should better support the use case of salting/peppering passwords. This means manually typing a short suffix at the end of important passwords, such that the suffix is NOT stored in the passwords manager. That way, if the master password is compromised the attacker will not have access to those passwords. The same suffix is used for all important passwords making it easy to remember. Here's a description of this practice:

https://passwordbits.com/salting-passwords/

This can be done with Proton, but unfortunately it recognizes the password was manually changed and constantly offers pop-up suggestions to store the new password. You can change the browser extension settings to stop the pop-ups for a domain, but this prevents storing a new password periodically. Actually there are separate settings for pop-up suggestions and storing new passwords, but frustratingly these are linked. So when you turn off the pop-ups it prevents the storage options from being selected. Seems like this could be easily fixed by keeping these two settings independent.