Until Winter 19, we cannot add data to the existing dataset, so the option:
1. Manually merge in Excel file
Download existing Einstein Analytics Order dataset into CSV file, manually combine with the latest quarter CSV file and existing Einstein Analytics. Then edit the dataset to Replace the data using combined CSV.
2. Using Append Transformation
Load the latest quarter CSV as a new dataset.
Create a dataflow to read existing dataset and append with the latest quarter CSV uploaded.
Register the combined data to the existing dataset.
append_Master node: "Source" is both dataset.
reg_Master node: set "Alias" with dataset API name for the master data, and "Name" with Name for master dataset.
You can check the dataset API name by edit the dataset.
yellow highlight is the dataset Name, which can be different with API name
green highlight is API name.
Make sure you just run the dataflow once, otherwise you will create duplication from Quarter data.