When adding a 3D cord lock, here are some important points to note:
Be sure to use a low grid size for the cord pattern pieces.
Check that the layer order of the 3D object is higher than the garment pattern pieces.
Exporting the cord lock as a U3MA for later use will keep the new line connectors so that they do not need to be re-applied when used again.
Why change the orientation of the 3D object?
The original direction of the trim shows the holes facing us. The line connectors need to be placed so they go through the holes. If we were to add line connectors as described but keep the original direction, the lines would show as dots in the 2D window, and we could not stitch to them with the stitch tool. This occurs because the axis where line connectors are placed doesn’t show in the 2D window.
For example, on the left is the line connectors added with the original 3D object orientation and on the right is the method shown in the video. The top row is the same trim as below but without texture showing for easier visibility. We can see that on the left, the line connectors show as dots.