Using spread operator on Firestore 'Value' field -- possible/not?

Hi! Sorry for the delayed response.

Yes, my formDataTransformer.value returns an object. It is a function that shapes the data model of the document that I will be saving to Firestore.

I've tried {{...formDataTransformer.value }} but it still return an error:

To give you a little bit more context:
I want to save a bunch of data and append a "updatedAt" timestamp into the document.
If I put the updatedAt inside the transformer, it will be converted into a string (not a Firestore object).

I know and have read this topic: http://community.retool.com/t/firestore-dates-written-as-strings-not-timestamps/2912, but it seems that we should declare every variable in the query's value field. But I can't do this since the values might differ in each query and I need the flexibility (by using spread, we don't have to retype every single variable that needs to be saved).

Any ideas on how to achieve this? Thanks in advance!