Make composer better or equal to competition
I like Proton Mail, but what makes it inferior to other competitor e-mail is its Composer. It is simply an effective "text message" editor.
It appears that all efforts are made to improve Proton Mail "technical" feature, but little effort is made to improve its useability at least at the same level of Outlook, Gmail etc.
Berygan shared this idea
A is, cannot compose decently designed business e-mails.