Currently you can delete unused custom fields one at a time. However, there is a select option, but when you select multiple custom fields to delete, the delete function disappears and the only option is to move them into another folder (Contact Info, General Info or Additional Info)

Surveys can get extremely cluttered when there are a lot of unnecessary custom fields (use case: loading a snapshot that has a lot of custom fields)

It is time consuming to have to delete unused custom fields one at a time instead of a Bulk Delete.