Hi pcng618,
By default all drop down custom elements from the Smart framework automatically determine the opening direction of the actual drop down depending on the space available. For example, if there’s not enough space for the drop down to open below the element it will open above it. Regardless you can set a specific position via the dropDownPosition property. Here’s a link to the API with all avaialbe options: modes
Example:

<smart-drop-down-list drop-down-position="top">
 <smart-list-item>A</smart-list-item>
 <smart-list-item>B</smart-list-item>
 <smart-list-item>C</smart-list-item>
</smart-drop-down-list>

Best Regards,
Christopher
Smart HTML Elements Team
https://www.htmlelements.com