Summary
It may be necessary to batch-create assignments based on existing datasets in Workforce for ArcGIS to be able to manage and review multiple datasets. Currently, there is no built-in tool to batch import data as assignments.
Procedure
It is possible to either manually append the data from an existing dataset, or to batch-create assignments using a Python script. For more information on how to batch-create assignments using the Python script, refer to the following Esri Github page.
To manually append the data, follow the instructions below.
- Open ArcGIS Pro and log in to ArcGIS Online with the ArcGIS account that created the workforce project.

- In Contents, add a .csv table containing unique IDs of the data and XY data or spatial dataset to the map.
- If the dataset is not spatially enabled, right-click the newly added table > Display XY Data.

- Ensure the X and Y fields are correct, and click Run. A temporary layer is added to the map.

- Right-click the newly added layer > Data > Export Features.
- Modify the output feature class name, and click Run. A new layer is added to the map.

- Remove the temporary event layer from the map.
- In the Catalog pane, click Portal, and open the workforce project folder. Locate the assignment layer in the folder.

- Drag and drop the assignment layer to the map.
- In the Geoprocessing pane, open the Append tool.
- Specify the parameters as follows:
- Input Datasets: The exported feature layer created in Step 2d
- Target Dataset: The assignment layer
- Schema Type: Select Use the Field Map to reconcile schema differences

- Ensure the required fields are mapped correctly, and click Run. The assignments are appended to the assignment layer.