I generate hide my email aliases for almost everything now
* newsletters, generic accounts I'm not attached to
* important accounts like utility provider

I would like an easy way to identify aliases that are important and be able to filter emails sent to those aliases.

The current approach works but is cumbersome. In Proton Pass configure a new mailbox that aliases could be forwarded to. I chose: my-address+papertrail@proton.me

Then, for important email aliases, forward them to "my-address+papertrail@proton.me".

In Proton Mail, use the filter UI to send any email sent to "+papertrail@proton.me" to a folder.

Next step: edit the filter with Sieve and add "X-Original-To" to the list of headers to match on. The condition then looks like

if anyof (address :all :comparator "i;unicode-casemap" :matches ["To", "Cc", "Bcc", "X-Original-To"] "*+papertrail@proton.me")

It works, but setting it up is cumbersome.

Filtering based on email alias in any capacity is a welcome addition. I would use it to protect myself against potential phishing attacks. For example, if I provide a particular alias to eBay and an email comes from ebay.support1info.com or something that impersonates the legitimate site, I could filter it into the phishing folder if the alias configuration were exposed to the ProtonMail filtering mechanism.

yes, definite must

This should absolutely be an option. How do you offer multiple aliases and yet you can't see each individual aliases email? Why force a user to sort through multiple aliases emails in one screen? It defeats the purpose of separation and encapsulation.