At the moment, if you want to create a new line you should use [Shift]+[Enter], which is a very uncommon shortcut for a new line shortcode.
What is happening is that people accidently click on [Alt]/[Options]+[Enter], thinking that it would make a new line, which is the most used keyboard shortcut on desktop OS and a lot of web apps for a new line. However, when they do that, it would actually perform an action, rather than going to a new line.
A solution would be to change [Shift]+[Enter] to [Alt]/[Options]+[Enter] for a new line OR
Make [Enter] to create a new line alone and do the action after clicking with the mouse.
That way much less accidental searches will happen, keeping people from wasting daily searches and helping them enter multiple keywords in the field itself without copy/paste from somehwere else.
It could help a lot with brainstorming. Try brainstorming with unconventional shortcut combination like [Shift]+[Enter], it just doesn't work.
So yeah, I think the preferred way is to make [Enter] to create new lines.