If you use live connection to import data, you cannot add other data source to Power BI,here are some ways you can refer to:
1.You can transfer the data mode to Direct Query First, then you can import other data source
Open the feasure in preview:
Then you can change the mode, you can refer to the following link:
Using DirectQuery for datasets and Analysis Services (preview) - Power BI | Microsoft Learn
2.Use import mode to imort ssas data at first, then you can add other data source.
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