src/vs/workbench/browser/contextkeys.ts/WorkbenchContextKeysHandler/updateSplitEditorsVerticallyContext
class WorkbenchContextKeysHandler:	private updateSplitEditorsVerticallyContext(): void {
		const direction = preferredSideBySideGroupDirection(this.configurationService);
		this.splitEditorsVerticallyContext.set(direction === GroupDirection.DOWN);
	}