Heads-up: This is only possible with Divi Areas Pro
Create or edit an Area via the wp-admin > Divi Areas editor.
In the Divi Area meta box, open the Behavior tab and open the section “Keep Closed”. All you need to do is enabling the Keep Closed behavior and you’re good.
Optionally, you can adjust the duration to keep the Area closed or changing the start event for the Keep Closed timer.