You don't need to do it through the email interface. You can do it through many password managers (API key). With simplelogin and a custom domain you can set it up to use regexes and control the flow of emails to any number of inboxes. It's like a fine grained catch-all where you don't need to create the emails ahead of time and can "send as" any of them... or disable any if they start receiving spam.

If I wanted to activate a new Facebook I could just type fuckbookNOV2023@customdomain.com into the signup field and verify it seconds later. If I wanted it to go to both me and my brother, I could add his custom string (e.g. fuckbookNOV2023bruzz@customdomain.com).

I've been doing this for 2 years and only recently received my first spam. All I had to do was change the email with the service and disable the old address. Easy peasy. You can also disable the catch-all at any time if someone starts fucking your life. Then all you have to do is create a dozen emails ahead of time and assign them as needed.

Also u/umbrella

Sorry, yes you do. Because it's so interlinked in my mind I got that wrong. But deffot the easiest way to do it I've found (as long as you're using proton mail though, I guess...)