This is critical for me. I don't want to have to waste time manually turning an email into a calendar entry, I should be able to do it seamlessly.

This needs to occur in all instances: web, mobile app, etc. If you get it on the Android you'll get the drop on Gmail; they still haven't enabled this ability in their Android app, you can only do it in their webmail client.

Ideally, Protonmail would recognise a 'calling notice' email and ask me if I want a calendar entry, plus it should try to populate the calendar entry itself but let me edit it.

I have waited years to use protonmail and calendar on my iphone. Please finally make the circle complete. I still have to wait until I get to a computer to make appointments. Why? It is 2023. Google did this years ago.

I want to be able to create an entry seemlessly without having to click the narrow part of the bottom after the day is populated. A suggestion:

One Click (an entry) - Displays event/details
Double Click (anywhere in the day area) - Creates an event
Left click - Displays options to view week, jump to a specific date, or search for an event

Exactly what Thomas said. Events added and default notification settings for events and having the ability to click event and see original email with details saves so much time.

The ability to create a Calendar entry directly from PMail with one click would be invaluable. Too much time is wasted cutting and pasting.