Q.Pests on magnolia
Something is eating my magnolia and the leaves appear to be eaten in a lace like manner. I keep scanning the tree to find what is eating the leaves, but I can’t see anything, though the leaves are left in a lace like pattern. The tree is in a large pot on the patio.

This could be Leaf Miners, or several other insects that dine on the leaves.
Treat with Neem Oil and I would treat weekly during the growing season to prevent further insect damage.
Here is a few links for you with more information.
https://www.gardeningknowhow.com/plant-problems/pests/insects/leaf-miner-control.htm
https://www.gardeningknowhow.com/plant-problems/pests/pesticides/neem-oil-uses.htm
https://www.gardeningknowhow.com/ornamental/trees/magnolia/magnolia-tree-care.htm