Hi @Yaswanth G Modals windows are not supported yet in constellation. 

Also pleas see this from QNA

Cosmos React is Data Model driven interface. But how to add something that isn't really related to the data? Like Modal Windows or Buttons?

You can run local actions there, so it is data driven or process driven. But you need to design it to view it. Modals are not yet supported.

You can post your questions on Ask the expert discussion here too.

Thanks.