Overview
Azure and Jira have a different approaches to item hierarchy.
While Jira allows for a three-level hierarchy (Subtask → Standard Work Item → Epic), Azure does not restrict the number of hierarchy levels, allowing for unlimited Parent-Child relations in a single hierarchy tree.
Visual representation of Azure hierarchy depends on chosen process and is up to 4 levels.
...
When neither Epic nor Subtask synchronization is enabled, Items Multi-level-hierarchy synchronization section serves standard link synchronization only (with forced Parent/Child link on Azure side).
...
Configuration > Mappings > Hierarchy:
<img here>
Azure → Jira: When Related To link is added in Jira between Story and Feature (custom type), then in Azure, there will be Parent/Child link created between corresponding User Story and Feature.
...
Configuration > Mappings > Hierarchy:
<img here>
Four level Azure configuration (Agile Azure DevOps process)
...
Configuration > Mappings > Hierarchy:
<img here>