How to set tag value for arrays

I'm not sure I understand the question. Can you please provide more details? I mean, metatags are always string values, aren't they?

Please check the attached photos.
How do I populate name and value fields in ECA "set tag value" if I want to override the schema product offer fields of schema metatag?

Sorry, I still don't understand. What is a "schema product offer fields of schema metatag"?

Are you able to set a meta tag of a normal Drupal page? How is that then different for what you're trying to do?

Yes, I am able to set many meta tag values but I am not able to set those that the fields are stored as serialised arrays in the database. An example is the product offers properties in schema product meta tag.

To reproduce this, install schema.org metatag module, activate it and try to set values for product offers.

Have you tried using dots or periods as separators for the key? That's often how these types of modules are separating the nested keys.

Thank you for your replies. I will try it and give feedback.

Dot separator isn't working. Only machine names work for me and I don't know how to implement it on serialized array field.