- the nested stack elements that are going to change, not only the parent ones
- the logical members/fields that prompt the change
from the changeset window. All this info they have, and should be trivial to show, which tells me they either don't use their own tooling (no dogfooding), or they have internal, better diagnostic tools not exposed to customers.
You should be pleased to hear that 'change sets for nested stacks' support was just released last week:
https://aws.amazon.com/about-aws/whats-new/2020/11/aws-cloud...
https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGui...
For others like me who were wondering why we didn't see this change:
https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGui...
create-change-set – Change sets for nested stacks is not enabled by default for the AWS CLI. To create a change set for the entire stack hierarchy, specify the --include-nested-stacks parameter. For more information, see To create a change set (AWS CLI).
Edit: grammar.