"Suddenly a darkness settled upon the land, so thick and black that it seemed a “darkness which may be felt.” Not only were the people deprived of light, but the atmosphere was very oppressive, so that breathing was difficult. “They saw not one another, neither rose any from his place for three days: but all the children of Israel had light in their dwellings.” The sun and moon were objects of worship to the Egyptians; in this mysterious darkness the people and their gods alike were smitten by the power that had undertaken the cause of the bondmen. [See Appendix, note 2 .] Yet fearful as it was, this judgment is an evidence of God's compassion and His unwillingness to destroy. He would give the people time for reflection and repentance before bringing upon them the last and most terrible of the plagues. PP 272.1"
"And the Lord said unto Moses, Stretch out thine hand toward heaven, that there may be darkness over the land of Egypt, even darkness which may be felt."
EGW directly quotes "darkness which may be felt" from Exodus 10:21 and elaborates on the effects of the darkness, staying very close to the biblical account.
"the Lord, until we come thither.” The king's anger burst forth beyond control. “Get thee from me,” he cried, “take heed to thyself, see my face no more; for in that day thou seest my face thou shalt die.” PP 272.2"
"And Pharaoh said unto him, Get thee from me, take heed to thyself, see my face no more; for in that day thou seest my face thou shalt die."
EGW directly quotes Pharaoh's words to Moses from Exodus 10:28, indicating a clear and intentional reference.