In QB desktop, on the item screen there is a check mark box for sub item of, check that and select the parent

Parent items should not be ordered or stocked in QBDT, they are just place holders to organize the listing

in QB each item is unique, you must order and […]

Resolution for 'Child items issue: 'Inventory: How do I set up Parent/Child items?' available: Yes.

The Child items issue or error code is a known issue in Quickbooks Online (QBO) and/or Quickbooks. Support for this issue is available either by self-service or paid support options. Experts are available to resolve your Quickbooks issue to ensure minimal downtime and continue running your business. First try to resolve the Child items issue yourself by looking for a resolution described in the article. If it is a complex Child items issue or you are unable to solve the issue, you may contact us by clicking here or by using other Child items support options.

For more information about resolving issues related to Child items in Quickbooks/QBO or to get support for the issue 'Inventory: How do I set up Parent/Child items?', click the link below: