documentclass{article}
usepackage{hyperref}
begin{document}
begin{Form}
PushButton[
  name =switch,
  onclick= {%
    var test = this.getField("test");
    if (test.display == display.visible) {
    test.display = display.hidden;
    } else {
    test.display = display.visible;
    }
  }
]{Switch visibility} \

TextField [name=test, value= I will disappear]{} \

TextField [name=other, width=textwidth, value= Can I take the place of the first field when it is hidden ?]{} \
end{Form}
end{document}