From California Native Plants for the Garden, a book I thought I'd read cover to cover several times, in regard to Venegasia carpesiodes:

Leaf miners occasionally tunnel through the leaves, creating intricate whitish patterns. The damage they do is primarily cosmetic, so think of the tunnels as nature's doodles and don't worry about the plant's health.

I've never put that spin on leaf miner damage before. Nature's doodles.