change-default-submit-button-text-per-level.php

<?php
/**
 * Change the default submit button text on the checkout page.
 *
 * You can add this recipe to your site by creating a custom plugin
 * or using the Code Snippets plugin available for free in the WordPress repository.
 * Read this companion article for step-by-step directions on either method.
 * https://www.paidmembershipspro.com/create-a-plugin-for-pmpro-customizations/
 */
function my_pmpro_change_default_button_text_per_level() {
	$checkout_level = pmpro_getLevelAtCheckout();

	switch ( $checkout_level->id ) {
		case '1':
			$submit_button_text = 'Your Custom Text for Level 1';
			break;
		case '5':
			$submit_button_text = 'Your Custom Text for Level 5';
			break;
		default:
			$submit_button_text = 'Create Account';
			break;
	}
	?>
	<span id="pmpro_submit_span">
		<input type="hidden" name="submit-checkout" value="1" />
		<input type="submit" id="pmpro_btn-submit" class="<?php echo esc_attr( pmpro_get_element_class( 'pmpro_btn pmpro_btn-submit-checkout', 'pmpro_btn-submit-checkout' ) ); ?>" value="<?php esc_html_e( $submit_button_text) ?>" />
	</span>
	<?php

	//show default checkout button
	return false;

}
add_filter( 'pmpro_checkout_default_submit_button', 'my_pmpro_change_default_button_text_per_level' );