As part of the current design, D365 does not allow to associate multiple hierarchies to the same workflow.

I tried using the sub workflow, but it errors out stating 'Failed to find subworklfow data'. This issue is occurring as the Related Action chosen, does not allow to pass reference to the same workflow.

The workflow should include a reference action which relates to the same workflow to address the issue as it is a common customer scenario where we need to have multiple level of approvals associated to different hierarchies.