In the main navigation you can create a drop-down menu.
Go to Layout > Navigation.
Follow these four easy steps:
1. In the main navigation, add the link that should be shown as a drop-down menu.
Click on Add link > Enter the name, e.g.: Category.
If you do not want this link to be clickable, select URL in the URL field and type “#”.
2. Create second navigation with the exact same name as the link you’ve just created.
3. Add all relevant links to your navigation. They will be displayed as a drop-down menu.
4. Check out how your drop-down menu looks like in your store: