We provide the way for customer create onepage website easy.
Create Menu for Onepage
Use menu normal to create Menu One page
Notice, we just need to use Custome Link type item for each menu which point to the inline content of page.
With menu item point to other page, you use as normal way.
Assign Section to Menu Items
To create a section for Menu Item, just add your rows from Visual Composer then assign ID of the row as URL anchor of Menu Item.
Then check your frontend.