Create row sequence based on row id column but retaining other column

Hi Anonymous , After the index did you expand it Could you try this please 

• Sort the Data:

  • Sort the table first by the Row_Id column in ascending order, then by Split_Desc in ascending order. This ensures a proper order for generating the sequence.

• Group the Data:

  • Group the data by Row_Id:
    • Go to Transform → Group By.
    • Group by Row_Id.
    • Create an All Rows operation to retain the grouped table.

• Add an Index for Sequencing:

  • Within each group, add an index to generate the Row_Sequence:
    • After grouping, click the small table icon for the grouped column.
    • Add an Index Column starting from 1.
    • Rename this index column as Row_Sequence.

• Expand the Table:

  • After adding the index, expand the grouped table to flatten it back into a single table:
    • Click on the expand icon next to the grouped column.
    • Include all original columns and the newly created Row_Sequence column.

let
  
    Source = Table.FromRows(
        {
        //Data
        },
        {"Row_Id", "Split_Desc"}
    ),
    
    // Convert data types
    ChangeTypes = Table.TransformColumnTypes(Source, {{"Row_Id", Int64.Type}, {"Split_Desc", Text.Type}}),
    
    // Sort by Row_Id and Split_Desc
    SortedTable = Table.Sort(ChangeTypes, {{"Row_Id", Order.Ascending}, {"Split_Desc", Order.Ascending}}),
    
    // Group by Row_Id
    GroupedTable = Table.Group(
        SortedTable,
        {"Row_Id"},
        {
            {"AllData", each Table.AddIndexColumn(_, "Row_Sequence", 1, 1, Int64.Type)}
        }
    ),
    
    // Expand grouped data
    ExpandedTable = Table.ExpandTableColumn(GroupedTable, "AllData", {"Row_Id", "Split_Desc", "Row_Sequence"})
in
    ExpandedTable
​

If this post helped please do give a kudos and accept this as a solution
Thanks In Advance