How do I show property definitions when a specific workflow state is triggered

You can use Medatada Card Configurator (MDCC) and set filter for that state and on behaviour you can set that property to show. IF you want only some people to see that property even when it's on that state, you can modify property definitions permissions to make it happen.

You can use Medatada Card Configurator (MDCC) and set filter for that state and on behaviour you can set that property to show. IF you want only some people to see that property even when it's on that state, you can modify property definitions permissions to make it happen.