Is it possible to set a default "from" email address for Epi forms and if so, how? I've read this comment and understand that it should be possible, but not exactly how.
Also, is it possible to lock this field and not make it editable?
Which one of these do you want to do:
I want this field to be predefined and not editable/hidden when selecting "send email" as the submit action on the form:
This should do it. Just follow one of these guides to create your own custom property for forms:
When you render it just add 'readonly' to it: https://www.w3schools.com/tags/att_input_readonly.asp