How to consider cracked section for composite section?

You can use the 'Section Stiffness Scale Factor' function. In your model, section stiffness scale factor is applied to take into account the creep effect of the concrete slab, which would not be necessary for the negative moment region if you want to ignore the slab stiffness. So, remove the section stiffness scale factor for the negative moment region and define new section stiffness scale factor to ignore the slab stiffness. The factor would be the ratio of the section properties between the 'reinforcement plus steel beam' and the 'slab + steel beam'. It should be manually calculated.

Alternatively,

There's an option for "Cracked Section" under the "Section manager" -> "reinforcement" which would consider the slab for stiffness calculation of the composite section. We can turn ON that option as well.