How to add custom registration plugin in my CUSTOM FOrm

Question

Hello I have one Custom registration filed plugin i want to add field in my custom form how can i do that? i share the code they use customer attribute to add field how can i add field in my custom form

$attributeObj->setData('used_in_forms', $usedInForms);
        $fieldset->addField(
            'used_in_forms',
            'multiselect',
            [
                'name' => 'used_in_forms[]',
                'label' => __('Display Fields in Form'),
                'title' => __('Display Fields in Form'),
                'values' => [
                    ['label' => __('Admin Customer Form'), 'value' => 'adminhtml_customer'],
                    ['label' => __('Customer Account'), 'value' => 'customer_account_edit'],
                    ['label' => __('Registration Form'), 'value' => 'customer_account_create'],

                    ['label' => __('Custom Registration Form'), 'value' => 'customer_index_index'],
                ],
                'required' => true
            ]
        );

Answer 1

app/code/Cm/Customer/Setup/InstallData.php

<?php
namespace Cm\Customer\Setup;

use Magento\Customer\Model\Customer;
use Magento\Framework\Setup\ModuleContextInterface;
use Magento\Framework\Setup\ModuleDataSetupInterface;

class InstallData implements \Magento\Framework\Setup\InstallDataInterface
{
    private $eavSetupFactory;

    private $eavConfig;

    private $attributeResource;

    public function __construct(
        \Magento\Eav\Setup\EavSetupFactory $eavSetupFactory,
        \Magento\Eav\Model\Config $eavConfig,
        \Magento\Customer\Model\ResourceModel\Attribute $attributeResource
    ) {
        $this->eavSetupFactory = $eavSetupFactory;
        $this->eavConfig = $eavConfig;
        $this->attributeResource = $attributeResource;
    }

    public function install(ModuleDataSetupInterface $setup, ModuleContextInterface $context)
    {
        $eavSetup = $this->eavSetupFactory->create(['setup' => $setup]);

        $eavSetup->removeAttribute(Customer::ENTITY, "skype");

        $attributeSetId = $eavSetup->getDefaultAttributeSetId(Customer::ENTITY);
        $attributeGroupId = $eavSetup->getDefaultAttributeGroupId(Customer::ENTITY);

        $eavSetup->addAttribute(Customer::ENTITY, 'skype', [
            // Attribute parameters
            'type' => 'varchar',
            'label' => 'Skype Account',
            'input' => 'text',
            'required' => true,
            'visible' => true,
            'user_defined' => true,
            'sort_order' => 990,
            'position' => 990,
            'system' => 0,
        ]);

        $attribute = $this->eavConfig->getAttribute(Customer::ENTITY, 'skype');
        $attribute->setData('attribute_set_id', $attributeSetId);
        $attribute->setData('attribute_group_id', $attributeGroupId);

        /*
        //You can use this attribute in the following forms
        adminhtml_checkout
        adminhtml_customer
        adminhtml_customer_address
        customer_account_create
        customer_account_edit
        customer_address_edit
        customer_register_address
        */

        $attribute->setData('used_in_forms', [
            'adminhtml_customer',
            'customer_account_create',
            'customer_account_edit'
        ]);

        $this->attributeResource->save($attribute);
    }
}
?>

app/code/Cm/Customer/view/frontend/templates/additional.phtml

<div class="field skype required">
    <label class="label" for="skype">
      <span><?= $block->escapeHtml(__('Skype Account')) ?></span>
    </label>
    <div class="control">
       <input type="text" name="skype" id="skype" value="" title="<?= $block->escapeHtmlAttr(__('Skype Account')) ?>" class="input-text" data-validate="{required:true}">
    </div>
</div>

app/code/Cm/Customer/view/frontend/layout/customer_account_create.xml

<?xml version="1.0"?>

<page xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" layout="1column" xsi:noNamespaceSchemaLocation="urn:magento:framework:View/Layout/etc/page_configuration.xsd">
    <body>
        <referenceContainer name="form.additional.info">
            <block class="Magento\Framework\View\Element\Template" name="form_additional_info_customer" template="Rsgitech_Customer::additional.phtml"/>
        </referenceContainer>
    </body>
</page>

you want to add a custom field as static refer this lik

otherwise you want to add custom field as dynamic field use this extension