src/vs/workbench/common/notifications.ts/NotificationViewItem/sticky
class NotificationViewItem:	get sticky(): boolean {
		if (this._sticky) {
			return true; // explicitly sticky
		}

		const hasActions = this.hasActions;
		if (
			(hasActions && this._severity === Severity.Error) || // notification errors with actions are sticky
			(!hasActions && this._expanded) ||					 // notifications that got expanded are sticky
			(this._progress && !this._progress.state.done)		 // notifications with running progress are sticky
		) {
			return true;
		}

		return false; // not sticky
	}