Need help pls (Hide/Show text with a button)

How about this…

$w.onReady(function () {
  $w("#button").onClick(() => {
    if ($w("#hiddentext").collapsed) {
      $w(`#hiddentext`).expand();
      $w("#button").label = "-";
    } else {
      $w(`#hiddentext`).collapse();
      $w("#button").label = "+";
    }
  });
});

Note: to be consistent with variable naming conventions in JavaScript, you might want to rename the element ‘hiddentext’ to ‘hiddenText’, using camelcase capitalization.

Here’s the result – before click and after click: