Control the component position

You can find some previous answers on how to throw components around in these two links:

I suppose in your case you could do something like:

html.Div(
   html.Div([
      dcc.Dropdown(id='the-first-one'),
      dcc.Checkboxes('blah'),
      dcc.Checkboxes('blah'),
      dcc.Checkboxes('blah'),
   ]),
   html.Div(
      dcc.Dropdown(id='the-second-one'),
      style={'display': 'inline-block'}
   )
)