Adding data to Vector Search Index

[someOne2]

I am familiar with vectordbs like weaviate and pinecone, and trying to migrate my vectors to gcp. I have uploaded data to a bucket, created index with it and deployed an endpoint using python and following this documentation Vector Search Quickstart.Querying works fine for the index.

Now I want to add new data to the same index, (batch upsertion or equivalent in weaviate or pinecone), which as far as i understand can be done via GUI by doing batch update in the edit Index option, but I am unable to figure out how can i achieve it with python client.

I apologise if this is stupid question, been trying to figure out for a while now, and docs are confusing me more than helping.

I looked at update and rebuild Index and updateIndex, but am unable to figure out if this creates entire index from scratch with the new data or upserts them like weaviate or pinecone.

ps: UseCase:
I want to be able to query my embeddings with text like, 'a dog' etc returning best matches.