Is any node available for Google Merchant Center?
I don’t believe there is an official node.
You can interact with the Merchant Center API using the regular HTTP node and OAuth2 Google credentials though.
Merchant center reference: Get started | Content API for Shopping | Google for Developers
Also possibly of interest, you can move Merchant Center data to BigQuery using data transfer, which can make it easily accessible for n8n, obviously only applicable if you are looking to get data and not do any operations on the merchant center.