src/vs/workbench/contrib/themes/browser/themes.contribution.ts/openExtensionViewlet
function openExtensionViewlet(paneCompositeService: IPaneCompositePartService, query: string) {
	return paneCompositeService.openPaneComposite(VIEWLET_ID, ViewContainerLocation.Sidebar, true).then(viewlet => {
		if (viewlet) {
			(viewlet?.getViewPaneContainer() as IExtensionsViewPaneContainer).search(query);
			viewlet.focus();
		}
	});
}