TLDR, hopefully this clears it up::

*** This request Defeats the very purpose of why Proton Authenticator MFA app even EXISTS in the first place in addition to Proton Pass. ***
TLDR:

*** Proton Pass already offers this requested "seamless" integration of autofillable password management and autofillable MFA codes in a single app ***

*** Proton Authenticator MFA app is designed to be used as a Very Deliberately Totally Separate app for MFA codes while NOT AT ALL using Proton Pass' or any other password manager's ability to generate and autofill MFA codes ***

So, Bottom Line is, by what's on Proton's website:

A.) If you want "seamless" autofilled login credentials + autofilled MFA codes in 1 app, just use Proton Pass app for both, as that's what it is designed for.

OR

B.) If you want some additional security against less common complex attacks, you gain that extra security by *Deliberately* choosing a little less convenient solution of a Deliberately separated MFA codes app from a password management app:

* use the Proton Authenticator app that is Deliberately Separate/Deliberately Not-connected-to-a-password manager for MFA codes, and manually type them in to use them

* while also using Proton Pass or other password manager for usernames and passwords credentials and autofilling them, while DELIBERATELY NOT using Proton Pass' ability to also generate and autofill MFA codes

NOTE:
Use Proton Authenticator app for your Proton account's MFA code, even if you choose to use Proton Pass for MFA codes with all your other accounts

https://proton.me/support/pass-2fa#:~:text=Please%20note%20that%20you%20should%20never%20use%20Proton%20Pass%20to%20secure%20your%20Proton%20Account%20using%20TOTP.%20Use%20a%20third%2Dparty%20authenticator%20app%20instead.

MORE:

* "Proton Pass or Authenticator? Choose the right 2FA for you
No one understands your online habits or security needs better than you — that’s why we give you the power to choose how to secure your accounts. We created Proton Authenticator even though Proton Pass already has a built-in 2FA authenticator feature so that you can choose a tool that works for you, regardless of your threat model.

For convenience: Proton Pass lets you autofill your 2FA codes with your passwords, making logins faster and easier.

For advanced security: Proton Authenticator generates your 2FA codes in a separate, end-to-end encrypted app. This adds an extra layer of security and protects against sophisticated attacks. It also gives you a standalone app you can use to set up 2FA for your Proton Account."

https://proton.me/blog/authenticator-app

* "I love Proton Pass, but I want a separate app for my 2FA codes"
While Proton Pass offers a built-in 2FA authenticator, using a separate secure authenticator app provides an extra layer of defense against sophisticated attacks.
https://proton.me/authenticator/security

* "How is this different from Proton Pass?
Proton Pass is a password manager designed to securely generate and store strong passwords, and protect your digital identity with features like email alises and dark web monitoring. It also includes an integrated authenticator that can store and autofill 2FA codes - but not the ones used to log in to your Proton account. Proton Authenticator is a standalone 2FA app that allows users to enable 2FA protection for their Proton account, it also allows users to store their 2FA codes separate from their passwords if they wish to do so."
https://proton.me/authenticator

ALSO:
* Proton could do a little bit better job explaining all of this in the App Store description. Most people aren't going to go to an app's website, but they willl sometimes feature request in areas where there's ambiguity.

i would love this just so easy to log in to places

a) Authenticator was made to be a separate product for security reasons, but can sync across devices.
b) This is in development: AutoFill

Would be nice if proton authenticator codes showed up in proton pass too

Also if one exports from Proton Pass after adding additional accounts, and imports again to Authenticator, with Sync on in Authenticator, ALL of the accounts are duplicated in Authenticator. Effectively, the Sync feature is useless.

It’s nice that we can export from Pass and import to Authenticator, but I agree that wholesale sync should be an option.

Currently, two-factor authentication must be exported from Proton Pass on desktop as a ZIP file then imported into Proton Authenticator. I add logins with 2FA to Pass regularly, so to have them available in Authenticator, I have to export after each addition. And export isn’t possible on Pass mobile, where I spend 80% of my day. Pass and Authenticator tap the Proton account, so they should sync related records.

Please add feature to sync 2fas from proton pass to authenticator.