Use macros of JetEngine in the Default Value area of Hidden, Text, Date, Time, Datetime, Colorpicker, and Number fields.

macros_in_default_value.php

<?php

class JFB_Do_Macros_In_Default {
    
    public function __construct() {
        add_action( 'plugins_loaded', array( $this, 'maybe_add_filter' ) );
    }
    
    public function maybe_add_filter() {
        if ( ! function_exists( 'jet_engine' ) ) {
            return;
        }
        add_filter( 'jet-form-builder/render/text-field', array( $this, 'do_macros' ) );
        add_filter( 'jet-form-builder/render/date-field', array( $this, 'do_macros' ) );
        add_filter( 'jet-form-builder/render/time-field', array( $this, 'do_macros' ) );
        add_filter( 'jet-form-builder/render/hidden-field', array( $this, 'do_macros' ) );
        add_filter( 'jet-form-builder/render/number-field', array( $this, 'do_macros' ) );
        add_filter( 'jet-form-builder/render/datetime-field', array( $this, 'do_macros' ) );
        add_filter( 'jet-form-builder/render/color-picker-field', array( $this, 'do_macros' ) );
    }
    
    public function do_macros( $args ) {
        $args[ 'default' ] = jet_engine()->listings->macros->do_macros( $args[ 'default' ] );
        return $args;
    }
    
}

new JFB_Do_Macros_In_Default();