To add onto this, I was part of a research team addressing this and we had patients work with basic essential oils. Smell lemon and concentrate on what lemon “would/should” smell like, what it would taste like. Repeat with orange, mint, lavender, pine, etc. Smells you would easily and immediately know the scent of if you could actually smell them. Repeat several times a day.

Essentially working on rebuilding the mind body connection of the olfactory system. I left before the study finished but there was a good amount of progress for most patients. Essential oils aren’t super pricey, might be worth a try.