Topic feed - Aggregate search and then provide the rest of the collection

Hi, I am currently trying to implement a complex database search using filtering & sorting from the client. Similar to how Social Network sites retrieve helpful & accurate data results.

I have built the filtering using a ‘what best matches’ to the clients category choices. However, once a user has scrolled through all of the relevant/matching results I dont want to tell them it is the end of the line and that is everything. I want to show them more that may not match their search options but may still interest them.

What I want to do:
So I was hoping to group (List #1) the returned list from the users search… and then append the rest of the collection (List #2) to the end of the first list excluding any items that have been retrieved from the first list.

This is the aggregation I am doing to get the First List:

db.collection.aggregate([
  {
    "$match": {
      "language": "eng",
      "category": {
        "$in": [
          "a",
          "b",
          "c"
        ]
      }
    }
  },
  {
    "$project": {
      "_id": 1,
      "title": 1,
      "bannerImg": 1,
      "description": 1,
      "user": 1,
      "roleCount": {
        "$size": "$roles"
      },
      "relevanceCount": {
        "$size": "$category"
      }
    }
  },
  {
    "$sort": {
      "relevanceCount": -1
    }
  }
])

Now I want to get everything else in this db collection and append it to the bottom of this list as other posts to look at.

Could I use $group to group first list and make a second list which removes group 1’s items and then I can run sorting and filtering algorithms on that? If so how would that be written?