In system.xml, add frontend model

<product_test_btn translate="label"> <frontend_model>mymodule/adminhtml_system_config_testbtn</frontend_model> <sort_order>87</sort_order> <show_in_default>1</show_in_default> <show_in_website>0</show_in_website> <show_in_store>1</show_in_store> </product_test_btn>

In your block, you can modify the html output, and you can add yr logic & load other required data here.

class Mycompany_Mymodule_Block_Adminhtml_System_Config_Testbtn extends Mage_Adminhtml_Block_System_Config_Form_Field {

/**
 * Generate button html
 *
 * @return string
 */
public function getButtonHtml()
{
    $button = $this->getLayout()->createBlock('adminhtml/widget_button')
        ->setData(array(
            'id'        => 'my_button',
            'label'     => $this->helper('adminhtml')->__('Send Product (Test)'),
            'onclick'   => 'javascript:check(); return false;'
        ));

    return $button->toHtml();
}
/**
 * Return element html
 *
 * @param  Varien_Data_Form_Element_Abstract $element
 * @return string
 */
protected function _getElementHtml(Varien_Data_Form_Element_Abstract $element)
{
    return $this->_toHtml();
}

In system.xml, add frontend model

<product_test_btn translate="label"> <frontend_model>mymodule/adminhtml_system_config_testbtn</frontend_model> <sort_order>87</sort_order> <show_in_default>1</show_in_default> <show_in_website>0</show_in_website> <show_in_store>1</show_in_store> </product_test_btn>

In your block, you can modify the html output, and you can add yr logic & load other required data here.

<?php 
    
class Mycompany_Mymodule_Block_Adminhtml_System_Config_Testbtn extends Mage_Adminhtml_Block_System_Config_Form_Field
{
    
     /**
     * Generate button html
     *
     * @return string
     */
     public function getButtonHtml()
     {
         $button = $this->getLayout()->createBlock('adminhtml/widget_button')
                ->setData(array(
                'id'        => 'my_button',
                'label'     => $this->helper('adminhtml')->__('Send Product (Test)'),
                'onclick'   => 'javascript:check(); return false;'
            ));

        return $button->toHtml();
    }
    /**
     * Return element html
     *
     * @param  Varien_Data_Form_Element_Abstract $element
     * @return string
     */
    protected function _getElementHtml(Varien_Data_Form_Element_Abstract $element)
    {
        return $this->_toHtml();
    }