One design, several systems, stacked.
A design can hold more than one system. Open the Layers flyout, add a layer, and it arrives with its own generator, its own parameters, its own seed. Select it and the whole control panel switches over, so you are only ever editing one system at a time.
Layers draw bottom to top, and each carries a blend mode. Multiply, screen, overlay, the usual set. Two flat systems put together this way will often make something neither of them could manage alone, which is the main reason to bother with more than one.
Scale, Offset X, Offset Y and Rotate sit at the top of the panel. They apply after the system has finished drawing, around the centre of the canvas, so the composition inside the layer never shifts. Two copies of the same system at different scales will read as depth for exactly this reason.
Rotating a layer does not leave bare corners. The area a layer needs to cover is worked out as the inverse image of the canvas, so the system simply keeps drawing until the gap is filled.
Add, delete and reorder from the same flyout. If you want a starting point rather than a blank one, I'm bored will sometimes hand you a stack of two to four layers, now and then with a couple of parameters already moving.