Thank you for your consideration.  The multi-select doesn't easily fit our needs since we are dealing with millions of rows of data and almost as many serial numbers. 

I will stick with the solution I already have which are:

  $(document).ready(function () {
        var grid = $("#grid").data("kendoGrid"); // Get an instance of the Grid
        var gridColumns = grid.columns; //get the current grid columns options
        gridColumns[1].filterable = { //set the "filterable" options of the 3rd column "SERIAL_NO"
            extra: false,
            operators: { //specify the operators that should be displayed in the column filter menu. Here you can review the available operators based on the field data type (date, number, string, enum): https://docs.telerik.com/kendo-ui/api/javascript/ui/grid/configuration/filterable.operators
                string: {
                    contains: "Contains",
                    eq: "Equal to",
                    startswith: "Starts With",
                    endswith: "Ends With",
                    neq: "Not Equal to",
                    doesnotcontain: "Doesn't contain",
                    doesnotstartwith: "Does not start with",
                    doesnotendwith: "Does not end with",

                }
            }
        };
        grid.setOptions({ //update the grid column settings
            columns: gridColumns
        });
    });

 

function onFilter(e){
  if(e.filter === null) {
     e.sender.dataSource.filter();
     //this will clear all
      //e.preventDefault()
      //e.sender.dataSource.filter({})
       } else {      
       //come here is not null and then if field is serial no
        if(e.field == "SERIAL_NO"){
          var operator = e.filter.filters.filter(x=>x.field == "SERIAL_NO")[0].operator;
           var searchcondition = (e.filter.filters.filter(x=>x.field == "SERIAL_NO")[0].value);
            var isComma = searchcondition.includes(",");
             e.preventDefault()
             e.filter.logic = "or";
            if(isComma) {
                const conditions = searchcondition.split(",");
                for(i = 0; i<conditions.length; i++) {
                    var c = conditions[i].trim();                    
           e.filter.filters.push({field:"SERIAL_NO",operator:""+operator+"",value: c})
                }

            } else {
                 e.filter.filters.push({field:"SERIAL_NO",operator:""+operator+"",value: e.filter.filters.filter(x=>x.field == "SERIAL_NO")[0].value})
            }
                 
            e.sender.dataSource.filter(e.filter);
        }
               }  //else e.filter is not null
    }                    

Thank you for asking.  I've attached a short mockup of a way I think it could be shown and additional information on how we are hacking to get the "IN".  If this does not provide the information you need, please let me know.

With the help of Telerik experts, I was able to hack the behavior of a SQL "In" condition by adding custom code to the cshtml page. For this particular application, all other column fields only use 1 value; only the serial number column needed multiple values beyond 2 values.

We will tell our users to enter multiple values comma-separated.  They will be using a copy/paste action from lists that come from our external customers. (This is an application to provide our external customers with test data on the components they have purchased from us & there will be many serial numbers included in the report.)

We also did a custom filter menu because for this application, we think having the And/Or will confuse the users since they have the ability to enter multiple items in any condition. A comma-separated list is turned into "OR" operators.

Here is the relevant code in what we are doing:

                    

<div id="griddiv">
    @(Html.Kendo().Grid<HPK_DATA>(Model.testdata)    
    .Name("grid")
    .Columns(columns => {
       columns.LoadSettings(Model.columns);
    })
    .Events(ev=>{
        ev.Filter("onFilter");
        //ev.FilterMenuInit("filterMenuInit");
    })
    .Pageable()
    .Sortable()
    .Scrollable()
    .Filterable()
    .Resizable(r => r.Columns(true))
    .DataSource(dataSource => dataSource
        .Ajax()
        .PageSize(20)
        .Read(read => read.Url(Url.Action()+"?handler=Read").Data("forgeryToken"))
     )
)
</div>

  $(document).ready(function () {
        var grid = $("#grid").data("kendoGrid"); // Get an instance of the Grid
        var gridColumns = grid.columns; //get the current grid columns options
      //  alert("This is gridColumns 2 " + gridColumns[1].title);
        gridColumns[1].filterable = { //set the "filterable" options of the 3rd column "SERIAL_NO"
            extra: false,
            operators: { //specify the operators that should be displayed in the column filter menu. Here you can review the available operators based on the field data type (date, number, string, enum): https://docs.telerik.com/kendo-ui/api/javascript/ui/grid/configuration/filterable.operators
                string: {
                    contains: "Contains",
                    eq: "Equal to",
                    startswith: "Starts With",
                    endswith: "Ends With",
                    neq: "Not Equal to",
                    doesnotcontain: "Doesn't contain",
                    doesnotstartwith: "Does not start with",
                    doesnotendwith: "Does not end with",

                }
            }
        };
        grid.setOptions({ //update the grid column settings
            columns: gridColumns
        });
    });

 

function onFilter(e){
  if(e.filter === null) {
     e.sender.dataSource.filter();
     //this will clear all
      //e.preventDefault()
      //e.sender.dataSource.filter({})
       } else {      
       //come here is not null and then if field is serial no
        if(e.field == "SERIAL_NO"){
           var operator = e.filter.filters.filter(x=>x.field == "SERIAL_NO")[0].operator;
          var searchcondition = (e.filter.filters.filter(x=>x.field == "SERIAL_NO")[0].value);
            var isComma = searchcondition.includes(",");
             e.preventDefault()
             e.filter.logic = "or";
            if(isComma) {
                const conditions = searchcondition.split(",");
                for(i = 0; i<conditions.length; i++) {
                    var c = conditions[i].trim();                    
           e.filter.filters.push({field:"SERIAL_NO",operator:""+operator+"",value: c})
                }

            } else {
                 e.filter.filters.push({field:"SERIAL_NO",operator:""+operator+"",value: e.filter.filters.filter(x=>x.field == "SERIAL_NO")[0].value})
            }
    e.filter.filters.filter(x=>x.field == "SERIAL_NO")[0].value})
            e.sender.dataSource.filter(e.filter);
        }
               }  //else e.filter is not null
    }