Magento – Create custom button on catalog > product page in admin panel

Create a file in Vendorname\Module\Block\Adminhtml\CustomButtom.php

<?php
namespace Vendorname\Module\Block\Adminhtml\Buttom;

use \Magento\Backend\Block\Widget\Context;
use \Magento\Backend\Model\UrlInterface;

class CustomButtom extends \Magento\Backend\Block\Widget\Container {
    protected $_backendUrl;

    /**
     * @param \Magento\Backend\Block\Widget\Context $context
     * @param array $data
     */
    public function __construct(
        Context $context,
        UrlInterface $backendUrl,
        array $data = []
    ) {
        $this->_backendUrl = $backendUrl;
        parent::__construct($context, $data);
    }

    /**
     * Block constructor adds buttons
     *
     */
    protected function _construct() {
        $this->addButton(
            'import_ref',
            $this->getButtonData()
        );
        parent::_construct();
    }

    /**
     * Return button attributes array
     */
    public function getButtonData() {
        $url = $this->_backendUrl->getUrl("module/page/index");
        return [
            'label' => __('Custom buttom label'),
            'on_click' => 'setLocation("'.$url.'")',
            'class' => 'primary'
        ];
    }
}

In your layout just need to add the buttom

Vendorname\Module\view\adminhtml\layout\name-layout.xml

<block class="Vendorname\Module\Block\Adminhtml\Status\CustomButtom" name="CustomButtom"/>

Add Following code in app/code/Vendor/Module/view/adminhtml/ui_component/category_form.xml

<?xml version="1.0" encoding="UTF-8"?>

<form xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Ui:etc/ui_configuration.xsd">
    <settings>
        <buttons>
            <button name="openModel" class="Vendor\Module\Block\Adminhtml\Category\Edit\AddModelButton"/>
        </buttons>
    </settings>
    <modal name="test_model">
        <settings>
            <options>
                <option name="buttons" xsi:type="array">
                    <item name="0" xsi:type="array">
                        <item name="text" xsi:type="string">Done</item>
                        <item name="class" xsi:type="string">action-primary</item>
                        <item name="actions" xsi:type="array">
                            <item name="0" xsi:type="array">
                                <item name="targetName" xsi:type="string">${ $.name }</item>
                                <item name="actionName" xsi:type="string">actionDone</item>
                            </item>
                        </item>
                    </item>
                </option>
                <option name="title" xsi:type="string">CUSTOM MODEL</option>
            </options>
            <onCancel>actionDone</onCancel>
        </settings>
        <fieldset name="general" sortOrder="10">
            <settings>
                <label/>
            </settings>
            <field name="test1" sortOrder="10" formElement="input">
                <settings>
                    <dataType>text</dataType>
                    <label translate="true">Test 1</label>
                    <dataScope>test1</dataScope>
                    <validation>
                        <rule name="required-entry" xsi:type="boolean">true</rule>
                    </validation>
                </settings>
            </field>
            <field name="test2" sortOrder="20" formElement="textarea">
                <settings>
                    <label translate="true">Test 2</label>
                    <dataType>text</dataType>
                    <dataScope>test2</dataScope>
                </settings>
            </field>
        </fieldset>
    </modal>
</form>

Add following code in app/code/Vendor/Module/Block/Adminhtml/Category/Edit/AddModelButton.php

<?php

namespace Vendor\Module\Block\Adminhtml\Category\Edit;

use Magento\Framework\View\Element\UiComponent\Control\ButtonProviderInterface;
use Magento\Catalog\Block\Adminhtml\Category\AbstractCategory;

class AddModelButton extends AbstractCategory implements ButtonProviderInterface
{
    public function getButtonData()
    {
        return [
            'label' => __('Open Model'),
            'class' => 'action-secondary',
            'data_attribute' => [
                'mage-init' => [
                    'Magento_Ui/js/form/button-adapter' => [
                        'actions' => [
                            [
                                'targetName' => 'category_form.category_form.test_model',
                                'actionName' => 'toggleModal'
                            ]
                        ]
                    ]
                ]
            ],
            'on_click' => '',
            'sort_order' => 20
        ];
    }
}

you will get what you looking for :D