To streamline this process, I developed a tiny Chrome extension that allows you to create a new masked email through the context menu with just one click, and autofill the email form field.
It’s a simple privacy-friendly tool - no telemetry, no servers, no tracking - and is open source on Github: https://github.com/tmarice/fast_masked_mail_creator/
I’d love feedback — especially from others who use masked emails daily or have multi-account Fastmail setups.