We know that some technology and software can perform automated network operation tasks, for example, DHCP in the Network layer and error coding (FEC) in the Link layer. I'm sure there are many more examples.

Based on the complexity of tasks, my question, is which OSI layers, i.e., Physical, Link, Network, Transport or Application (see the OSI Reference Model illustrated for more information) are network managers more inclined to focus their manual operations? Or are we as NMs concerned with all layers equally?

I'm only after a general idea of which layers NMs tend to be involved in, such as VLANs in a MAC address configuration. I'm not looking for detail on each individual OSI layer.