getElementCustomProps(el) {
    const props = {};
    Object.keys(el).forEach((key) => {
      if (key.startsWith("_")) return;
      props[key] = el[key];
    });
    return props;
  }
Get target custom properties - only shows custom props not element default ones
Excludes custom props starting with _
@param {HTMLElement} el Target element
@returns {object} Object of propname/value pairs