Here was our approach with my Grandma who had Parkinson's and LBD - we let her eat anything she wanted, whenever she wanted, but only gave her a small amount at a time - think 1/4 cup, a few bites. It was not perfect, she had anything but a balanced diet, but it got the food in.

Her favorites were tinned sardines and oysters for a period, then (mixed together) peanut butter and jam on shortbread cookies. Also ice cream, or frozen custard, which is actually quite nutritious. And canned fruit cut in small bites. We also figured out that is someone sat with her and ate the same things as she did, a little more food was eaten.

Interestingly, my daughter was a nurse in a Memory Care, and that was one of their dietary strategies - seeing others eating seemed to spark a recall of food/eating/sociability and was actually one of the best times of day for her residents. They made a special French toast, bread soaked overnight in cream & eggs, then lightly baked. They made 2 flavors to cater to taste - one sprinkled with cocoa mix and the other with cinnamon. A few of her residents ate only that for weeks on end.

My Mom had post-stroke memory & eating issues - we gave her malts made of protein drinks with chocolate ice cream.

Just a few ideas - I apologize if you have already tried them, but I know how frustrating it is to get food in.

Wishing you a calm day!
Sue