This is critical to me, too. Using the meeting Lock function is not the same as selective admission of persons from a Waiting Room -- Lock is the sledgehammer solution for access control, and Waiting Room is the surgical scalpel solution.

Further, it's simply unreasonable to expect the Host to be able to:
(1) Check his/her IMs/emails outside Meet for requests to be admitted from legitimate guests who are locked out;
(2) Reply to those persons to advise that the meeting will be Unlocked and that they should attempt to Join again;
(3) Unlock the meeting with such amazingly lucky and precise timing that it is open when those legitimate guests happen to attempt to Join again, but not when any uninvited persons or Kicked Out guests happen to try to do the same, the timing of which will be unknown to the Host; and
(4) Police the collection of newly admitted attendees -- after they've already gained access to the secure meeting -- to ensure that only legitimate guests were admitted and Kick Out any interlopers...all while
(5) Successfully running the meeting he/she called
...all at the same time, without seriously risking compromising the meeting's security -- an impossible burden for any Host that Meet forces upon all Hosts.

Important so we can know who is knocking outside the meeting room

This is an essential feature. I cannot transition to Proton Meet until this is implemented.

this is a hugely needed feature for security for online classrooms and professionalism for work.

An Upvote to Samuel Ryan's Comment

This is also a necessary component for adoption as a teacher. I have to be able to admit people at the correct time, and also not admit people who have not paid or who have behaved abusively. Very anxious to see this added so I can drop Zoom!

This is the most important feature of a software like this. I like most others I know will not adopt this until that’s done and working well.

I want to second this exactly.

Problem: Currently, Proton Meet has permanent rooms that are great for recurring workflows (e.g., schedule management with EHR systems like Sessions Health). However, they lack a proper gatekeeper function. For users working under HIPAA regulations, a permanent link with only password gating is a liability. If a client joins five minutes early while a previous session is still active, they could accidentally "crash" a private meeting. This creates a significant privacy breach risk.

Proposal: Introduce a Waiting Room / Lobby feature specifically for permanent rooms. The host receives a notification when someone attempts to join. Pending joiners remain in a "holding state" with a customizable message until the host manually admits them. Ideally, this would include a toggle ability allowing hosts to turn the Waiting Room on or off in the meeting settings.

While Proton has a significant advantage with privacy by design instead of by promise, this current limitations is unfortunately enough to prevent Proton Meet adoption for this use case.