How to expand sub buttons in a vertical menu on click?

To expand sub buttons on hover go to the menu's advanced mode. Then check the collapse & click done. 
The result is that when you click over a button it will take you to the next page, and then all of it's sub buttons will appear.

Here is how to expand sub buttons in a vertical menu on click:

Step 1: Enter the vertical menu's edit mode

Step 2: Click advanced

Step 3: Check both check boxes - 'collapse' & 'collapse on click' (in red)


Note: Make sure you are on the Menu tab within General