Hi @elasticuser7 ,
No, you cannot search multiple site search engines in a single query. I'm not sure I've ever heard a request for this before - why not have 1 engine that just has your multiple domains?
Our other product, Elastic App Search, does allow you to create "Meta Engines", which allow a facade of a single Engine over multiple Engines. And with our latest version of Elastic App Search (7.12), we've introduced a beta Crawler. But before we talk through whether you should try that out, can you help me understand your usecase? Would just crawling multiple domains in your single engine solve your issue?