Have you taken a try with the Power Query functionality within CDS to import your Excel table data?
If you want to import Excel table data into a CDS entity within PowerApps, you could consider take a try with the Power Query functionality to achieve your needs.
Above import solution could only import Excel files data from OneDrive or OneDrive for Business folder, you need to upload your resource Excel file into your OneDrive or OneDrive for Business folder firstly.
In addition, you could also consider take a try with the "Open in Excel" functionality within the CDS entity. Firstly, you should open your target CDS entity where you want to import data into, then click "Open in Excel" option, then it would open a Excel file automatically. After that, you could copy your data from your resource Excel table, and paste them into the opened Excel file, then click "Publish" button to upload your data.