Data Explorer is not able to search in Stack exchange community search box. I think Data Explorer is not a community, is it?
The Stack Exchange Data Explorer (SEDE) is a dump of the SE databases.
From that databases all non-public information is stripped and then pushed to the SEDE database.
Using that database, you can write your own queries to get some insights you can't get from the sites themselves. Often users use this to come up with very nice diagrams or nice insights in how the sites actually work.
So, to answer your question, "is it a community": No. It is not. It is just a dump from all sites' databases. There is no Q/A, etc.