[{"metadata":{"custom_metadata":[{"key_id":"6052e700dc84ef7d492b5d30","type":"freetext","value":["desh","Fauji"]}],"tag_ids":[],"category_id":"5a02e20a23dfee730bbd7f4f",}}]

db.collection.update({},{"$set":{"metadata.custom_metadata.$[].value.$[value]":"Desh ki Dharti"}},{arrayFilters:[{"value":"desh"}]})