Hi @MarvinBangert
I agree with @Pstork1 . Currently, the Form control is not supported to customize the layout as you want.
As an alternative workaround, I recommend customizing layout by three edit forms. They are all from the same data source but with the respective data cards.
When you submit the Forms, Try to use the code:
If(Form1.Mode=FormMode.New,Patch('Data Source',Defaults('Data Source'),Form1.Updates,Form2.Updates,Form3.Updates),Form1.Mode=FormMode.Edit,Patch('Data Source',<Put Forms' Items property here>,Form1.Updates,Form2.Updates,Form3.Updates)) //repalce <> part by the Items property code of Forms

Hope this helps.
Sik