Hi @Syndicate_Admin
When you create a report with an excel file, these tables are in Import mode. While if you create a report with a PBI dataset, it is in Live Connect mode. You are not able to switch an table in Import mode into Live Connect mode. This is by design. Meanwhile, when you use a PBI dataset in Live Connect mode in a report, this report can only have this data source and are not allowed to add other data sources. It also means that when you already have other data sources in a report, this report is not able to add a Live Connect PBI dataset as a data source.
The only exception to use a PBI dataset and other data sources in a report at the same time is to use dataset in DirectQuery mode. This is a preview feature currently and you need to check corresponding option in File > Options and Settings > Options if you want to use it. See below references:
DirectQuery for Power BI dataset: How does it work? - RADACAD
Using DirectQuery for datasets and Azure Analysis Services (preview) - Power BI | Microsoft Docs
However, for your scenario, using PBI dataset in DirectQuery mode cannot solve your problem either because an import table cannot be swithed into DirectQuery mode.
I think a workaround is to publish your report into the service to get a new PBI dataset. Then create a new report in Power BI Desktop, connect to this dataset to create a report from scratch. (Or you can try copying all visuals from original .pbix file into this new one. I haven't tested this but you may refer to this blog: How to point existing reports to a new dataset in Power BI (even from AAS) - Kasper On BI) Now this report is in Live Connect mode. Then you can go to Data source settings to switch the data source to use another PBI dataset which have the same table structures.
Kindly let me know if this helps.
Community Support Team _ Jing
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