The key is
reduce.
The following variant of your jq program produces the output shown below:
reduce ("secrets","toto","test") as $k (.;
if index($k) | not
then . + {($k): $k}
else . end)
Output:
{
"config-maps": [
{
"map-data": {},
"config-map-label": "some stuff",
"config-map-name": "some other stuff"
}
],
"secrets": [
{
"aa": "*******"
}
],
"toto": "toto",
"test": "test"
}