Here is what the Mayo Clinic says about CoQ10
https://www.mayoclinic.org/drugs-supplements/coenzyme-q10/background/hrb-20059019
Background
Coenzyme Q10 (CoQ10) is an antioxidant that is made in the human body. CoQ10 is needed for basic cell function. CoQ10 levels decrease with age and may be low in people with cancer, certain genetic disorders, diabetes, heart conditions, HIV/AIDS, muscular dystrophies, and Parkinson's disease. Some prescription drugs may also lower CoQ10 levels.
CoQ10 in the body can be increased by taking CoQ10 supplements. There is evidence that idebenone, a man-made compound similar to CoQ10, may help treat Alzheimer's disease. However, evidence is lacking to support the use of CoQ10 itself for this condition. There is some evidence to support the use of CoQ10 for high blood pressure and heart failure.
Promising uses of CoQ10 include eye disease, chest pain caused by exercise, asthma, chronic fatigue, and high cholesterol, as well as the treatment of chemotherapy side effects in children.
Evidence is conflicting for the use of CoQ10 in heart muscle problems and exercise performance. There is some negative evidence for the use of CoQ10 in the treatment of diabetes, hepatitis C, and Huntington's disease.