A new documentation is available for Squash TM 2.0 and later versions, check it here
You may add a native requirement sub-hierarchy as the sub-hierarchy of a synchronized requirement.
For instance, a certain User Story in JIRA could possibly need several test requirements within Squash TM. Those test requirements need to be created under the synchronized requirement which represents this User Story within Squash TM.
Consequently, reporting in JIRA will be made over the whole requirement hierarchy and all test cases to which it is linked.