You could prepare all the data items and then call 'loadData' method to re-bind the new data.

Code:

var data = $('#cc').combobox('getData');
data.push({id:'idvalue',text:'textvalue'});
$('#cc').combobox('loadData', data);

Please download the newest 'datagrid-scrollview.js' file from http://www.jeasyui.com/extension/datagridview.php

Please add the style below to the page to prevent from greying the tab title.

Code:

<style>
.tabs-disabled{
  opacity:1.0;
}
</style>

If you do not want the user to select all the tabs, you can hide the tabs header.

Code:

$('#tt').tabs({
  showHeader:false
});

Please call 'disableTab' method to disable a special tab panel. When a tab panel is disabled, users can not click to select it but this tab panel still can be selected by calling 'select' method.

Code:

var t = $('#tt');  // the tabs object
t.tabs('disableTab', index);  // disable the special tab panel
t.tabs('select', index);  // select this tab panel again

The 'detailFormatter' function only provide the detail content container. You can append any contents to this container.

If you only want to use the datepicker plugin of jQuery UI with EasyUI, yes, they can work together. You can find the example here:
http://jsfiddle.net/qX26t/

Some conflicts may occur when using easyui with jQuery UI together. Please try to use the datebox plugin of easyui.

When calling 'load' method to load form combobox, the 'setValue' method of combobox will be called to set the combobox with new value, the related item of drop-down will be selected too.
Please see this example http://jsfiddle.net/YBhB9/.

Make sure that you are using the newest datagrid-filter.js file. If not please update this newest file to your page. After that, if your issue continues, please provide an example to demonstrate your issue.

After update a row, you need to call .linkbutton() to create the linkbutton again.

Code:

$('#dg').datagrid('getPanel').find('a.easyui-linkbutton').linkbutton();

The 'formatter' function only returns the formatted string. This function can't create any components automatically. You have to construct them manually. Please try to call .linkbutton(...) when loaded data successfully.

Code:

$('#dg').datagrid({
  onLoadSuccess:function(){
    $(this).datagrid('getPanel').find('a.easyui-linkbutton').linkbutton();
  }
});

The local searching is similar to this tutorial. All you need to do is to filter the 'data' and call 'loadData' method to render the new rows. Please see the 'doSearch' function to learn how to achieve this functionality.

Code:

function doSearch(q){
    var rows = [];
    $.map(data, function(row){
        for(var p in row){
            var v = row[p];
            if (String(v).indexOf(q) >= 0){
                rows.push(row);
                break;
            }
        }
    });
    $('#dg').datagrid('loadData', rows);
}

Here is the tutorial shows how to add search functionality.
http://www.jeasyui.com/tutorial/datagrid/datagrid24.php

The appendRow method append a new row to the current page. To append to other page, you have to change the grid page before calling this method.

You have to use draggable and droppable plugins to achieve this functionality manually.