The first question is which QuickBooks product you actually use. Advice written for one edition, region or year can be wrong for another. Start in your current account and the matching Intuit documentation.
Intuit's current global project guidance describes both project tracking and a Retainage setting. Older US support discussions describe a separate account and invoice item. Those sources do not prove that every account has the same features, and they should not be collapsed into one universal instruction.
This article previously said that QuickBooks had no retainage field and could not associate balances with jobs. Those claims were too broad. The useful question is what your configured system can report today, and what work remains outside it.

