Is there an option in GitLab which enables feature branch/merge request creation by default whenever an issue is created?
I know it is possible to create them manually by clicking that fancy button on the issue page, but let's face it, we're lazy...
I don't think that option already exists - as you mentioned there is the fancy button but I don't think there is a way to click it automatically if you will.
One drawback of this would be that every issue, even those you may not end up implementing, would get a branch.
Could you open an issue to discuss this possibility?