How can I allow customers to change the location of text on the live preview?

You can setup the live preview to allow your customers to visually drag the location of a text layer as shown below:

Layer setup

On the live preview layer, open the "Advanced" tab:

Set the location to "Interactive":

Advanced settings

The interactive location setting can be combined with the other advanced settings.

Position: Automatic/Manual.  The position is updated if the customer has not yet modified the location. 

Scale:  Automatic = always scales the font to fit the defined area (disable "Scale up" for use with text-editor).  Manual = font size is fixed or changed via the text-editor.  

Area: Full/Box . Defines the area where the layer can be moved around. 

Restrict dimensions

You can combine the Area=Box setting with the Location=Interactive setting:

With this setup, the text cannot be moved outside of the defined area:

Testing

Close the layer to test the interactivity inside the app: 

Interactive Actions

On the Advanced tab, you can enable the interactive actions tooltip that will appear when the customer selects the object on the preview:

Index Up / Down

The Index action allows moving the layer position in the stack to show behind or in front of other layers.

Note: Layers cannot be moved behind or in front of another layer that does not have the interactive Index action enabled. This allows preventing the customer from moving the layer behind a protected layer.

Dynamic Options

Duplicate and Delete actions are only supported for layers controlled by Dynamic Options.