If a product attribute has multiple features, you have to represent them properly. In the following post, we describe how to do this. More tips are available here: Magento 2 Developer’s Cookbook.
There is only one requirement for configuring multiple attribute values and it is related to the separator. While comma is widely used to split different parameters in a CSV files, this separator doesn’t work for multiple attribute values. You should use a pipe separator instead, which is represented by this character – “|”. See the following example:
where features is the attribute and Smart, UHD, and 3D are its values.
Alternatively, use third-party import extensions for Magento 2.