Thanks for your question. I want to make sure I understand what you want to do before I give you a detailed answer.
It looks like you want to populate the ALT Text field of images that are attached to a parent post/page with a list of the terms assigned to the parent post/page in the WordPress Tags taxonomy. Is that right? If so, I can give you some ideas on how to do that. If I haven’t understood the question, any additional information you can supply will be helpful. Thanks!
It has been a month since my last post in this topic. I hope you have found a solution for updating your ALT Text values.
I am marking this topic resolved, but please update it if I can be of any assistance with this task. Thanks for your interest in the plugin.