Mongo Playground

Configuration

[{"_id":"blablabla","UUID":"50ED0565C5BF","Email":"foobar@bar.ca","FirstName":"Bacel","LastName":"ELbs","ClientID":"sa-sa","UserSettings":{"dateRangeMode":"1","skillsMode":"1","CalendarViewMode":"One Month"},"Filters":[{"Type":"Calendar","Filter":[],"DefaultFilterID":""},{"Type":"Calendar","desc":"test","Filter":[],"isDefault":false}]}]

Query

db.collection.update({UUID:"50ED0565C5BF"},{$push:{Filters:{Type:"Calendar",desc:"test",isDefault:false,"Filter":["a","b","c"]}}})

Result