The big issues is that it takes multiple steps to tie a bow and MD simulates everything at once, so it would be really problematic to tie a bow in MD the same way one would in real life.
The cheaty way it to take two stripes one small one long, stick the small strip one layer above the long one, stitch each strip to itself on the far ends. Of course you'll need to stitch the smaller strip to something so it doesn't just float off. Then when you simulate you'll get the middle knot with the loopy ends and you can always stitch
...but ya like MIstahMoose it's easier to just model it.