I'm working on something. Yes, it is not recommended but could you please share if there is a way that you know of to add the nodes in jcr repository at in runtime?

No. Not exactly hiding or showing fields. But when the dropdown value ex: "great" is selected, it is mapped to a OOTB component. According to that mapping we have to create a node at runtime. 

Can we create nodes in the cq dialog at runtime?The requirement is the dialog initially would only have a single dropdown with few fixed fields. So, when an option from the dropdown is selected let's say a value great is selected so when this action happened in the dropdown now it should map the val...