Use Shopify Tags to Filter Customers
Shopify's customer tags are assigned as custom properties to the Klaviyo Profile of each customer who is synced into Klaviyo through the Shopify integration. Klaviyo will create a single "Shopify Tags" property, which is stored as a list data type (vs. a string). This is because when these tags are used there are often several tags applied to the same customer.
The string data type is used to collect a single word or single phrase (i.e. any plain text). The list data type is used when you want to collect an array of words/phrases, where each single item in the array can be identified individually.
The most common use-case for this list data type is when different tags are being collected as a single property, such as the Shopify Tag property. This allows you to use the property in a segment or filter, and then include as many available tags as you'd like as the property value.
For a flow filter, you can also use the "is not in" condition along with the String data type: