you can not
all you can do is print the BOM, one at a time, and export that screen to excel
google for ccrqbom – third party utility for assembly items
Resolution for 'BOM table issue: 'How do I output the BOM table/data for all Assembled items to Excel?' available: Yes.
The BOM table 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 BOM table issue yourself by looking for a resolution described in the article. If it is a complex BOM table issue or you are unable to solve the issue, you may contact us by clicking here or by using other BOM table support options.
For more information about resolving issues related to BOM table in Quickbooks/QBO or to get support for the issue 'How do I output the BOM table/data for all Assembled items to Excel?', click the link below: