vendure/packages/graphiql-plugin/src/ui/overrides.css

.graphiql-container.embedded-mode {
    --sidebar-width: 0px;
    border-radius: var(--border-radius-12);
}
.graphiql-container.embedded-mode .graphiql-sidebar {
    padding: 0;
}

.graphiql-container.embedded-mode .graphiql-sessions {
    margin: 0;
}

.graphiql-container.embedded-mode .graphiql-logo {
    display: none;
}