In Microsoft Dynamics 365 Finance and Operations, you can customize certain properties of existing Extended Data Types (EDTs) using the extension framework. This allows you to make adjustments without modifying the original object.
Editable Properties via Extension
You can change the following properties on EDTs through an extension:
Label
Help text
Form help
Country/Region codes
String size (only if the EDT does not inherit from another EDT)
Decimal precision (NoOfDecimals property)
You modify the properties as you would for newly added elements, using the property sheet.

After compiling the code, you can see the changes in the application.

You can view the created extensions in the Application Explorer in Visual Studio.

When the Same EDT Is Extended in Multiple Models
If the same Extended Data Type (EDT) is modified in more than one model (for example, by different ISVs), the system will apply the changes from the model with the highest Model ID in the same layer—typically the USR layer.
Example:
ISV 1 updates the
ItemId
label to “Awesome item number” in a model named AwesomeModel (Model ID: 15).ISV 2 changes the same label to “Super item number” in SuperModel (Model ID: 12).
Since AwesomeModel has a higher Model ID (15), its label change will take precedence. As a result, the user interface will display “Awesome item number”.