How to auto collapse all submenus

On smaller screens, when the user clicks on the menu icon, i would like him to see all submenus already collapsed (Example: the Activello theme does that). Whats the code I have to add please?

Hey there,

I hope you are well today and thank you for your question.

Code for this isn’t readily available,
You can request this drop down be added as a feature request here:

Best regards,