Using Trifacta, you can access tables stored in BigQuery datasets in different projects from the Dataprep service.
When you open the Import Data screen in Trifacta, the BigQuery tab automatically shows datasets and tables that are present in the same project as the Dataprep service. You can change the GCP project that contains your BigQuery data by clicking on the BigQuery link inside the Choose a table window:
This will take you into the BigQuery project selector. In the box that reads, "Go to Project", type the ID for your desired GCP project:
Double-check that you have typed the project ID correctly. Once you have entered the project ID, click Go to switch into the new project.
The Choose a table window has now updated to show the selected project in the BigQuery path:
As long as your permissions are set correctly in BigQuery, you can use Trifacta to work with tables from multiple BigQuery projects.