Not able to add 2 additional columns into Dataflow Gen2 as the source excel file has 2 columns added

mcrreddyt I think what you need should be possible, ref. https://community.fabric.microsoft.com/t5/General-Discussion/Dropping-and-recreating-lakehouse-table/m-p/3836094/highlight/true#M6322

For loading the columns from Excel to the Dataflow, maybe it helps to mark the content area in Excel as a Table, and point the Dataflow to the table, instead of referring to Excel sheet name in the dataflow. 

Otherwise, I think in the Advanced Editor in the dataflow maybe you need to adjust the number of columns to import from the Excel sheet.