Custom Property Tab -- List Default Value

Is it possible to have a default / initial value assigned to the List type property in custom property tab WITHOUT changing the start part template? 

I seem to only able to assign a default value to property that use Textbox but not List...

Example Scenario: 

1. The Start Part / Asm template is blank without the custom property 

2. User open Custom Property Tab and click Apply without changing the default value in the List 

     → User only need to change the List value if they wan a non-default value. 

I understand the most easiest way is to change the Start Part template, but i am just trying my luck here . 

Thanks.