Set the KUBECONFIG envar with all YAML files in the specified folder.

set-kubeconfig.sh

#!/bin/sh
DEFAULT_CONTEXTS="$HOME/.kube/config"
if test -f "${DEFAULT_CONTEXTS}"
then
  export KUBECONFIG="$DEFAULT_CONTEXTS"
fi

CUSTOM_CONTEXTS="$HOME/.kube/custom-contexts"
mkdir -p "${CUSTOM_CONTEXTS}"

OIFS="$IFS"
IFS=$'\n'
for file in `find "${CUSTOM_CONTEXTS}" -type f -name "*.yml" -or -name "*.yaml"`
do
  export KUBECONFIG="$file:$KUBECONFIG"
done
IFS="$OIFS"