When every post of a topic is merged to another topic, the post is automatically closed. Is there any way to have it also automatically unlisted?
No, that is not possible nor planned at the moment.
How can we request it.
How would people know what happened to the original topic if it mysteriously disappears.
How could they differentiate between posts being moved and a topic being deleted?
In our use case, we have a category that requires topic approval so that we can merge new submissions to avoid duplication. When we merge a topic, we merge the entire thing and the system automatically closes the topic. We then unlist it so that it does not pollute searches. We are just trying to save the extra step of having to manually unlist.