@(Html.Kendo().OrgChart<OrgChartEmployeeViewModel>()
                .Name("departmentsChart")
                .Editable(edit =>
                {
                    edit.Form(form => form
                      .Items(i =>
                      {
                         i.Add().Field(x => x.ParentDepartment).EditorTemplateView(Html.Partial("~/Views/Shared/EditorTemplates/ParentDepartmentDropDown.cshtml"));
                      }));
                })
                ...
)

// ~/Views/Shared/EditorTemplates/ParentDepartmentDropDown.cshtml
@model OrgChartEmployeeViewModel

@(Html.Kendo().DropDownListFor(m => m.ParentDepartment)
    .OptionLabel("-None-")
    .DataTextField("Text")
    .DataValueField("Value")
    .DataSource(source =>
    {
	    source.Read(read => read.Action("ReadDepartments", "Home"));
    })
)