QB Issue Resolution:

on the create new account screen, or the account screen when you edit, there is a check mark box on the right side “sub account of” and select the parent

I have no idea how many sub accounts you can have, desktop is 5

Resolution for Issue 'How do I create multiple sub-accounts under one account and how many can I create?' available: Yes (Solved).
Source: Intuit Community forum.

How do I create multiple sub-accounts under one account and how many can I create?: this 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 issue yourself by looking for a resolution described below. If it is a complex issue or you are unable to solve the issue, you may contact us by clicking here or by using other support options.

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