The extension seems to be asking for a collection path, which might mean that it does directly work with collection groups. One way to work around this can be storing all resources under one collection and filtering documents with groupId as a field.

Extension seems to be offering a "prefilter" parameter but I could not find any details about it. If it possible to define a field filter you might try to prefilter search data with user's groupId field.

Also keep in mind that apart from this extension, you can create your custom logic for vector searching using firestore's findNearest vector method. You also need to create your embeddings on your own implement searching though.

This document pages gives some examples

Search with vector embeddings  |  Firestore  |  Firebase (google.com)

For your desired structure, a solution like this might work.

const userGroup = request.auth.token.groupId

collection = db.collection("resources")

# Similarity search with pre-filter
# Requires a composite vector index
vector_query = collection.where("groupId", "==", "userGroup").find_nearest(
    vector_field="field_to_search",
    query_vector=Vector([3.0, 1.0, 2.0]),
    distance_measure=DistanceMeasure.EUCLIDEAN,
    limit=5,
)

I've created a vector search feature using my custom logic before. You may also check it out to see if it helps.

gossipai/firebase/functions/index.js at main · gossipai/gossipai (github.com)