This jq module includes a set of functions that are useful, to me, @pschmitt and maybe to you.
Grab ./plib.jq and put it in jq's include path.
kubectl get nodes -o json | jq -er -L "$PWD/plib.jq" \
--argjson cols '[".metadata.name", ".metadata.labels"]' '
import "plib" as p;
.items[] | p::getallpaths()
'
# Output
# {
# "metadata.name": "mynode-001",
# "metadata.labels": {
# "beta.kubernetes.io/arch": "amd64",
# "beta.kubernetes.io/os": "linux",
# "kubernetes.io/arch": "amd64",
# "kubernetes.io/hostname": "mynode-001",
# "kubernetes.io/os": "linux"
# }
# }