How to set custom primitive default value and modify single actor's value?

Excuse me. I’m using CustomPrimitiveData to make materials model. I want to set default value for my parameter. But when I search answer from documents and webs, I only find the way to set default value in blueprint construction script. It will make a question that when I want to modify single actor’ s material’ s custom primitive data, it is invalid. Because when I modify a actor’s property, It will br reconstructed and cover my modify. So I’m doubt that wheather there is a way to set the default value more confident and useable.

Thanks for you attention.