Inserting rows recursively does not yield correct results

There are a number of other issues in that code still. M is a functional language, and in those variables are typically immutable and you are trying to re-assign values to an existing variable which will not work. I'm not entirely clear on what it is you are trying to achieve. But to add a list of rows to a table you could use a pattern combining Table.Combine and List.Generate

 

The following example starts off with a single row and generates 3 new rows with incrementing dates.

 

eg

 

let
    nDate = #date(2021, 5, 19),
    nLoop = 3,
    nMaxIndex = 10,

    // Create inital row
    Initial ={[DateValue=nDate, Unique Dates=nDate, New.1=0, Active.1=0, Closed.1=0, Resolved.1=0, Accepted.1=0, Next ER.1=0, In Development.1=0, In Test.1=0, Pending Defects.1=0, Awaiting Acceptance Criteria.1=0, Ready for Development.1=0, Ready for Test.1=0, Proposed.1=0, Index=nMaxIndex]},
    tbl = Table.FromRecords(Initial),
    
    // Combine the initial data with the generated records
    Source = 
        Table.Combine({tbl, 
            Table.FromRecords( 
                // Generate a list of records
                List.Generate(
                    () => [DateValue=Date.AddDays(nDate,1), 
                        Unique Dates=Date.AddDays(nDate,1), 
                        New.1=0, 
                        Active.1=0, 
                        Closed.1=0, Resolved.1=0, 
                        Accepted.1=0, 
                        Next ER.1=0, 
                        In Development.1=0, 
                        In Test.1=0, 
                        Pending Defects.1=0, 
                        Awaiting Acceptance Criteria.1=0, 
                        Ready for Development.1=0, 
                        Ready for Test.1=0, 
                        Proposed.1=0, 
                        Index=nMaxIndex],
                    each [Index] < nMaxIndex + nLoop,
                    each [Index = [Index] + 1, 
                        DateValue= Date.AddDays([DateValue],1),
                        Unique Dates=Date.AddDays([DateValue],1), 
                        New.1=0, 
                        Active.1=0, 
                        Closed.1=0, 
                        Resolved.1=0, 
                        Accepted.1=0, 
                        Next ER.1=0, 
                        In Development.1=0, 
                        In Test.1=0, 
                        Pending Defects.1=0, 
                        Awaiting Acceptance Criteria.1=0, 
                        Ready for Development.1=0, 
                        Ready for Test.1=0, 
                        Proposed.1=0]
                )
            )}
        )
in
    Source