When you choose to add another Form 1099-SA, there should be a question or a check box that asks who the form belongs to. This should show up before you are asked to enter the details from the Form 1099-SA. All of the Form 1099-SA entries are in the same place, not really associated with the other HSA entries that are separated by which person is covered by the HDHP.
If you still do not see it, please share what version of TurboTax you are using so someone can take a closer look and try to guide you in greater detail.
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