Is it possible to use multiple datasets with the same structure on the same Preparation using only the Data Preparation Tool or is it only possible using the Talent Data Fabric?
Just to clarify: you want to re-apply a preparation created atop a given dataset on another dataset which has the exact same structure, correct? If so, that is doable in Data Prep, both in the Free Desktop and commercial versions. Once you opened the second dataset, look for the flask icon left to the "Export" button in the header bar and it will allow you to select the compatible preparation:
Introduction to Talend Open Studio for Data Integration.
Practical steps to developing your data integration strategy.
Create systems and workflow to manage clean data ingestion and data transformation.