src/vs/workbench/contrib/debug/browser/debugToolBar.ts/registerDebugToolBarItem
const registerDebugToolBarItem = (id: string, title: string | ICommandActionTitle, order: number, icon?: { light?: URI; dark?: URI } | ThemeIcon, when?: ContextKeyExpression, precondition?: ContextKeyExpression, alt?: ICommandAction) => {
	MenuRegistry.appendMenuItem(MenuId.DebugToolBar, {
		group: 'navigation',
		when,
		order,
		command: {
			id,
			title,
			icon,
			precondition
		},
		alt
	});

	// Register actions in debug viewlet when toolbar is docked
	debugViewTitleItems.push(MenuRegistry.appendMenuItem(MenuId.ViewContainerTitle, {
		group: 'navigation',
		when: ContextKeyExpr.and(when, ContextKeyExpr.equals('viewContainer', VIEWLET_ID), CONTEXT_DEBUG_STATE.notEqualsTo('inactive'), ContextKeyExpr.equals('config.debug.toolBarLocation', 'docked')),
		order,
		command: {
			id,
			title,
			icon,
			precondition
		}
	}));
};