The steps for preparing test returns for the purpose of comparing married filing joint and married filing separate are different in TurboTax Online and TurboTax Desktop/Download.
Please see here for the Desktop/Download steps.
To prepare test returns in TurboTax Online, In TurboTax Online, you'll need to create a test account separate from your regular TurboTax account and create a test return there. We recommend adding "test" or similar to your user ID so you can easily distinguish it from your actual account.
If you have set up separate returns using separate TurboTax Online accounts, or following the steps for the Desktop/Download version saving the data files with separate file names, then you should be able to both itemize on the separate returns.
Click here for more information about filing jointly versus separately.
Click here for tax tips for community property states. If you live in a community property state (Arizona, California, Idaho, Louisiana, Nevada, New Mexico, Texas, Washington, and Wisconsin), you will need to divide your community income according to the rules of your state.
See here for more information if you later decide to contact TurboTax directly.
[Edited 02/20/23| 2:48pm PST]
@andre_sidler
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