new dynamic formdata pass dynamic parameter

You have to cycle your forms. You can make an arrangement of forms with their respective IDs, or you can give them a class to everyone and cycle the class.

I'll give you an example cycling the class.

//Event cuando de click al botón
$(document).on('click','#btn',function(){
  var arr = [];
  //Recorremos todos los formularios
  $('.forms').each(function(){
    //Saca el formData del formulario actual
    arr.push( {data: new FormData( $(this) )} );
  });
  
  console.log( arr );
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

<form class="forms" method="POST" action="foo.php">
  <input type="text" name="foo">
</form>

<form class="forms" method="POST" action="bar.php">
  <input type="text" name="bar">
</form>

<form class="forms" method="POST" action="poo.php">
  <input type="text" name="poo">
</form>
<input type="button" value="Guardar todos" id="btn">

now in the button I put the parameter of the form ID in this case is save1, in the other would be save2

<button type="button" id="2" onclick="guardar('<?php echo 'guardar1'?>','<?php echo base64_encode('guardar')?>');">Guardar</button>


function guardar(g,f){
$(".loader").fadeIn("fast", function(){
    $.ajax({
        url: 'index.php?f='+f,
        data: new FormData($("#"+g)[0]),
        type:  'post',
        cache:false,
        contentType: false,
        processData: false,
        success:  function(resultado){
            if(resultado === "OK"){
                $("#pMensajeCorrecto").html("Registro guardado");
                $("#divMensajeCorrecto").show();
                modalPrincipal.modal("hide");
                setTimeout(function(){cerrar("divMensajeCorrecto");}, 3000);
                $('#tabla').click();
                $(window).scrollTop(0);
            }
            else{
                $("#pMensajeModal").html(resultado);
                $("#divMensajeModal").show();
                setTimeout(function(){cerrar("divMensajeModal");}, 3000);
                $("#divGuardar").scrollTop(0);
            }
            $(".loader").fadeOut("fast");
        },
    });
});

}