Hot off the presses, a little good news about anosmia, loss of smell. https://archive.is/dqhGD
tldr: While colds, flu, sinusitis can all cause loss of smell due to one mechanism, obstruction and swelling, Covid 19 has another mechanism. It attacks the substrate supporting the olfactory nerves. This can even lead to loss of the peripheral olfactory nerves. The somewhat good news is that they regenerate. The not so good news is that it takes a long, long time. And though it doesn't say so here, possibly in some cases the substrate destruction can't be overcome.
Just a thought. Various posts here have advocated spraying a very dilute solution of either hydrogen peroxide or iodine up the nose to kill the virus there. This will probably prevent the damage if sprayed, say, twice a day at the first sign of soreness.
(Not much help if you already have the problem.)