Adding new index

updated code:

let
    Source = Folder.Files("C:\\Umasankar\\Tenders\\B&R"),

    // Extract folder metadata
    #"Inserted Tender Name" = Table.AddColumn(Source, "Tender Name", each Text.BetweenDelimiters([Folder Path], "\", "\", 6, 0), type text),
    #"Inserted Company" = Table.AddColumn(#"Inserted Tender Name", "Company", each Text.BetweenDelimiters([Folder Path], "\", "\", 5, 0), type text),

    // Remove unnecessary columns and clean up
    #"Removed Columns" = Table.RemoveColumns(#"Inserted Company",{"Content", "Date accessed", "Attributes", "Folder Path"}),
    #"Removed Duplicates" = Table.Distinct(#"Removed Columns", {"Tender Name"}),

    // Load old indexed data (replace with actual query or table reference)
    OldData = YourOldIndexedTable,

    // Find new rows (anti-join)
    NewRows = Table.NestedJoin(#"Removed Duplicates", "Tender Name", OldData, "Tender Name", "OldData", JoinKind.LeftAnti),

    // Add new index to new rows
    #"Added New Index" = Table.AddIndexColumn(NewRows, "Index", Table.RowCount(OldData) + 1, 1, Int64.Type),

    // Combine old and new data
    CombinedData = Table.Combine({OldData, #"Added New Index"}),

    // Final cleanup (optional)
    #"Sorted Data" = Table.Sort(CombinedData, {{"Index", Order.Ascending}})
in
    #"Sorted Data"

Key Notes:

• Replace YourOldIndexedTable with your query or table reference that holds the old indexed data.
• The JoinKind.LeftAnti ensures only new rows are indexed.
• The Index for new rows starts from the last index of the old data (Table.RowCount(OldData) + 1).
  
  
  

for further reference please visit https://support.microsoft.com/en-us/office/add-an-index-column-power-query-dc582eaf-e757-4b39-98e6-bb59ae44aa82