I literally did this just yesterday for the first time. I want to write a blog post about this at some point, but since you're asking now I'll describe my approach below. Hold on to your hat, as it requires custom code and is quite involved.

As far as I know this sort of query currently can't be built with the FlutterFlow UI for backend queries. Firestore supports this sort of condition, but the FlutterFlow UI doesn't let you build the query.

So what I did is

Create a custom action that builds the query for Firestore
The custom action then listens to the snapshots() stream for that query
By listening for snapshots() we can show realtime updates in our UI. If you don't need that, the below can probably become a lot simpler.
When a snapshot is available, the custom action:
1. Converts the documents in that snapshot to a Map
2. Exposes the resulting List<Map> as a parameter to the callback that you can pass to the custom action
3. This Map can then be used as a JSON data type in the FlutterFlow UI
I then call this custom action in the page load event
Implement the callback (which is just another action flow in the FlutterFlow UI) to set the List<Map> into the page state
Then I bind my ListView to dynamically generate children for the List<Map> in the page state
And finally, I can bind a Text view in the list items to a JSON path in the Map/ JSON of the document

Note: if you have a custom Firestore type for the collection, you can use that instead of the Map / JSON that I used above, I was just trying to keep my code generic (as I'm hoping to turn this into a library at some point).

These are the action settings for my custom complexFirestoreQuery action:

And the code:

Future complexFirestoreQuery(\n    Future Function(List<dynamic> documents) onSnapshot) async {\n  final db = FirebaseFirestore.instance;\n  final currentUserUid = FirebaseAuth.instance.currentUser?.uid;\n\n  print('Starting snapshot listener on chat2 collection...');\n  db\n      .collection(\"chat2\")\n      .where(Filter.and(\n        Filter.or(\n          Filter(\"isApproved\", isEqualTo: true),\n          Filter(\"uid\", isEqualTo: currentUserUid),\n        ),\n        Filter(\"isDeleted\", isNotEqualTo: true),\n      ))\n      .orderBy(\"timestamp\", descending: true)\n      .limit(10)\n      .snapshots()\n      .listen((snapshot) {\n    final documents = snapshot.docs.map((doc) {\n      final map = mapFromFirestore(doc.data());\n      map['\\$id'] = doc.id;\n      return map;\n    }).toList();\n    print('Got ${documents.length} documents from Firestore, calling action.');\n    onSnapshot(documents);\n  });\n}

So my query reads chat messages that are either approved or by the current user, but skips all messages that have been deleted.

The Future Function(List<dynamic> documents) onSnapshot) in the code turns into an action flow in FlutterFlow. Here is how we invoke the custom action on page load and then hook up that onSnapshot callback/action flow:

As said earlier, the action flow here \"just\" updates a chat2list page state variable that I defined for this as a list of JSON objects:

Hang in there, we're almost at the end!

I then set the Generate Dynamic Children for a list view to build off of this chat2list variable:

And then finally bind text fields to JSON path $.message (the message field from the document) and to $[\"$id\"] the ID of the document that I stuffed into the Map too in the custom action code above:

As I warned at the start, it's quite involved - so let's hope that FlutterFlow soon allows its query builder to create such conditions (or allows us to add our own conditions in custom code without needing a full custom action).

Multiple Firestore Query Collection Filtering