and after that adding custom properties in jcr:content node of this template. After doing this, while I'm trying to create the translation project, those custom added properties are not reflecting in project.
Have you introduced application logic in your Workflow step to read these new properties. If so - how are you doing so. I want to make sure that there is business logic somewhere making use of these new props.
These new props I'm going to read in the workflow custom process step. I've written custom process step as part of translation workflow that triggers whenever I create a new translation project. So, on execution of workflow, custom process will fetch props values from payload jcr:content and based on the further code is written.