import panel as pn
pn.extension()

w1 = pn.widgets.TextInput(name='Text:')
w2 = pn.widgets.FloatSlider(name='Slider')

box = pn.WidgetBox('# WidgetBox', w1, w2)
box

w3 = pn.widgets.Select(options=['A', 'B', 'C'])
box.append(w3)

box