The "validate" button on https://tools.wmflabs.org/shex-simple/wikidata/packages/shex-webapp/doc/shex-simple.html?data=Endpoint:%20https://query.wikidata.org/sparql&hideData&manifest=&textMapIsSparqlQuery&schemaURL=https%3A%2F%2Fwikidata-shex.wmflabs.org%2Fwiki%2FSpecial%3ASchemaText%2FO2 in the first step does not actually validate but fetch the list of entities to be checked based on a query. So It should be renamed to say "run query to fetch entities". Once the query has been run it should say "validate entities".
* There is a clearly graspable two-step process of first fetching the entities and then validating them.
Ideally, when the user edits the query again afterwards (which means that the next Ctrl+Enter will fetch results again), the button label should update accordingly; if this turns out to be too much work, we can instead simply change the button label to some static string that’s always correct, e. g. “fetch query results or validate (Ctrl+Enter)”.