@John Connor - Thanks for reaching out.
Currently a tag key can only have one string field as the value. Since it is only this one text field, a user cannot list multiple different strings in array, but you can append to the string if needed. So, for example: If it is "CostCode" as the Key, the value is "123". To add an additional value to this, you would need to have a value like "123,234".
Product team is working on a new feature to allow an array of values to be created, but that will be later in 2022.
Hope that helps.
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