A 69-year-old woman with moderate COPD (post-bronchodilator FEV₁ 55% predicted) has persistent dyspnoea and two moderate exacerbations in the last year despite adherence to a dual long-acting bronchodilator inhaler (LABA/LAMA). She continues to smoke 5 cigarettes per day. According to CTS COPD pharmacotherapy guidance, what is the most appropriate next step?