360° Twirl 4D is in the Distortion category of Alex4D 360° Effects:
Here is what the Final Cut Pro 360° viewer and the viewer look like when the 360° Twirl 4D effect is applied:
Twirl controls how much the pixels are twisted around the Centre.
Size and Centre control the size and position of the twirl, which can also be set using the on-screen control.
This effect can work across large areas, but if you make Size larger than the height of the clip, the effect will not distort the 360° sphere correctly. To see when the distortion is too extreme, turn on Overlays. The colours used in the grid overlay can be changed the Horizon Colour and Grid Colour parameters. In this case, as the twirl is of a dark area of the clip, Grid Colour is set to red.