I found this article in pub Med

Conclusion: Non-inflammatory tracheal hypersecretion, not yet reported in COVID-19, may be an additional long-term symptom. The hyperstimulation of tracheal goblet cells secreting mucus is 1 pathophysiological hypothesis.

Learning points: Painless, non-inflammatory tracheal hypersecretion, which has yet to be described in post-acute COVID-19, may be an additional long-term symptom of the disease.The hyperstimulation of mucus-secreting tracheal goblet cells by the coronavirus, leading to tracheal discomfort and a feeling of suffocation, is 1 pathophysiological hypothesis.