Hi,
You can use complex collision by changing the collision complexity to UseComplexAsSimple. You can do this in the static mesh editor for the specific mesh you’re talking about.
One limitation with this is that the complex collision cannot be physically simulated. This means that things like gravity and momentum will not be computed for the body. However, in the case of your cereal bowl this would still allow the cereal (presumably balls) to simulate and interact with the complex collision.
If you want both concave and full physical simulation you’ll need to use multiple convex shapes. You can do this in the static mesh editor by using convex mesh decomposition.
Hope that helps