Using the Appearance panel to make a dashed line

You can use the Appearance panel to change the attributes that make up the object. You are able to change the colour of the fill, stroke, it's opacity, it's colour mode and add effects to change its appearance.
So the example shown here has a 2pt black stroke and no fill.

You can also add multiple attributes, all in the same object. These attributes can be treated like layers.

Moved one above the other enabling you to change the stacking order.

So the example below is still one object, just with three individual strokes applied. Black at 5pt, Yellow at 10pt and Red at 20 pt.

The visibility of each layer can be turned on or off by clicking on the eye icon.

You can see here in the next image how I have managed to crate the illusion of a dashed line.

You will need to set the Dashed line above the solid line and make it slightly wider. If it's the same size even you will see a slight outline around the clear or white part.

The main problem with this method is that the dashed line will work when over a white background or whatever colour the dash is in, but not work if over a different colour. In this example the green shape.

You also can't have true stitch lines with rounded ends, only square end caps or Butt Caps.

To create a double stitch line you will need to reverse the layers. The dashed line below and the solid line above.