Unfortunately, at this point the curve is strictly two dimensional, and we need to disturb it along the Z-axis in order to create a proper braid.  While you could make the spline editable and start pushing and pulling control points, that's very messy.  What we need is a formula plugged into the Z parameter of the Formula spline, to make the values of the Z coordinates match the shape we want.  The length-wise cross section of a braid is a figure eight - that is, each strand of the braid loops one way, and then the other.  I racked my poor atrophied mathbrain and realized that the original sine wave formula already plugged in by default is nearly what we want, with a small change:

100.0Sin(t2*pi)

This gives us a reasonable figure eight cross section like so.

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