Patch 

# https://*.com/questions/41958475/getting-the-object-array-index-in-jq
# https://www.codegrepper.com/code-examples/javascript/jq+array.length
kubectl get ds calico-node  -n kube-system -o json |jq '.spec.template.spec.containers[0].env | length'
kubectl get ds calico-node  -n kube-system -o json |jq '.spec.template.spec.containers[0].env |map(.name == "IP_AUTODETECTION_METHOD") | index(true)'
kubectl get ds calico-node  -n kube-system -o json |jq '[ .spec.template.spec.containers[0].env | debug | .name == "IP_AUTODETECTION_METHOD" ] | index(true)
kubectl get ds calico-node  -n kube-system -o json |jq '[ .spec.template.spec.containers[0].env | debug | map(.name == "IP_AUTODETECTION_METHOD") ] | index(true)'

LEN=`kubectl get ds calico-node  -n kube-system -o json | \
  jq '.spec.template.spec.containers[0].env | length'`
IDX=$((LEN-1))
IDX=`kubectl get ds calico-node  -n kube-system -o json |jq '.spec.template.spec.containers[0].env | \
  map(.name == "IP_AUTODETECTION_METHOD") | index(true)'`

DS=calico-node

CMPATH=/spec/template/spec/containers/0/env/$IDX/value
VAL="cidr=192.168.10.66/24"

kubectl patch ds/$DS -n kube-system --type='json' -p '[
  {"op":"replace","path":"'"$CMPATH"'","value": "'"$VAL"'"},
]'

 

Add

NM=IP_AUTODETECTION_METHOD
CMPATH=/spec/template/spec/containers/0/env/-
kubectl patch ds/$DS -n kube-system --type='json' -p '[
  {"op":"add","path":"'"$CMPATH"'","value": {"name": "'"$NM"'", "value": "'"$VAL"'"}},
]'