Add extra metadata to each message of a GRIB file?

I wonder, is there a tool to allow one add an extra metadata to each message of a GRIB file?
For example: from grib_dump of a GRIB file, I have:

#==============   MESSAGE 6 ( length=976330 )              ==============
GRIB {
  editionNumber = 1;
  table2Version = 2;
  # Rome  (RSMC)  (common/c-1.table)  
  centre = 80;
  generatingProcessIdentifier = 131;
  # None Wind speed m s**-1 (grib1/2.0.2.table)  
  indicatorOfParameter = 32;
  # Fixed height above ground height in meters  (2 octets)  (grib1/3.table)  
  indicatorOfTypeOfLevel = 105;
  level = 10;
  # Average  (reference time + P1 to reference time + P2)  (grib1/5.table)  
  timeRangeIndicator = 3;
  # Unknown code table entry ()  
  subCentre = 98;
  paramId = 500025;
  #-READ ONLY- cfNameECMF = unknown;
  #-READ ONLY- cfName = unknown;
  #-READ ONLY- cfVarNameECMF = ws;
  #-READ ONLY- cfVarName = ws;
  #-READ ONLY- units = m s**-1;
  #-READ ONLY- nameECMF = Wind speed;
  #-READ ONLY- name = Wind speed (SP_10M);
  decimalScaleFactor = 0;
  dataDate = 20201026;
  dataTime = 0;
  # Hour (stepUnits.table)  
  stepUnits = 1;
  stepRange = 0;
  startStep = 0;
  endStep = 0;
  #-READ ONLY- marsParam = 32.2;
  shortName = sp_10m;
  GDSPresent = 1;
  bitmapPresent = 1;
  numberOfVerticalCoordinateValues = 0;
  Ni = 928;
  Nj = 448;
  latitudeOfFirstGridPointInDegrees = 60;
  longitudeOfFirstGridPointInDegrees = -18;
  earthIsOblate = 0;
  uvRelativeToGrid = 0;
  latitudeOfLastGridPointInDegrees = 32;
  longitudeOfLastGridPointInDegrees = 40;
  iScansNegatively = 0;
  jScansPositively = 0;
  jPointsAreConsecutive = 0;
  #-READ ONLY- alternativeRowScanning = 0;
  jDirectionIncrementInDegrees = 0.063;
  iDirectionIncrementInDegrees = 0.063;
  #-READ ONLY- numberOfDataPoints = 415744;
  #-READ ONLY- numberOfValues = 308091;
  missingValue = 9999;
  tableReference = 0;
  #-READ ONLY- binaryScaleFactor = -19;
  #-READ ONLY- referenceValue = 0.529586;
  sphericalHarmonics = 0;
  complexPacking = 0;
  integerPointValues = 0;
  additionalFlagPresent = 0;
  packingType = grid_simple;
  bitsPerValue = 24;
  values(415744) =  {
  9999, 9999, 9999, 9999, 9999, 
  9999, 9999, 9999, 9999, 9999, 
  9999, 9999, 9999, 9999, 9999, 
  9999, 9999, 9999, 9999, 9999, 
  9999, 9999, 9999, 9999, 9999, 
  9999, 9999, 9999, 9999, 9999, 
  9999, 9999, 9999, 9999, 9999, 
  9999, 9999, 9999, 9999, 9999, 
  9999, 9999, 9999, 9999, 9999, 
  9999, 9999, 9999, 9999, 9999, 
  9999, 9999, 9999, 9999, 9999, 
  9999, 9999, 9999, 9999, 9999, 
  9999, 9999, 9999, 9999, 9999, 
  9999, 9999, 9999, 9999, 9999, 
  9999, 9999, 9999, 9999, 9999, 
  9999, 9999, 9999, 9999, 9999, 
  9999, 9999, 9999, 9999, 9999, 
  9999, 9999, 9999, 9999, 9999, 
  9999, 9999, 9999, 9999, 9999, 
  9999, 9999, 9999, 9999, 9999
  ... 415644 more values
  } 
  #-READ ONLY- numberOfCodedValues = 308091;
  #-READ ONLY- maximum = 17.9256;
  #-READ ONLY- minimum = 0.529586;
  #-READ ONLY- average = 5.81554;
  #-READ ONLY- numberOfMissing = 107653;
  #-READ ONLY- standardDeviation = 3.87567;
  #-READ ONLY- skewness = 0.861793;
  #-READ ONLY- kurtosis = -0.237433;
  #-READ ONLY- isConstant = 0;
  gridType = regular_ll;
  #-READ ONLY- getNumberOfValues = 415744;
}

There are 100 messages from this GRIB file. I want to add an extra metadata processingLevel=x with values for x from 1:100 (each message has an unique number).