Your supervisor refuses to let you change your seat because you want to sit away from someone who has Covid, what should you do?

You should realize that your request is rather ridiculous, as the person had COVID months ago, so would no longer be contagious or pose a risk. Asking to sit away from them would be like saying someone had the flu in December so you don’t want to sit near them in case you might get the flu from them.

If you want to quit your job because you are otherwise unhappy with the work environment, feel free to do so. Nobody is holding you hostage. If you think you can get another position paying similar money fairly quickly given your limited qualifications and geographic area, then maybe it’s your best answer if you don’t like it there. But it is generally a bad idea to quit a job without having another lined up. And you would not be able to qualify for unemployment or the pandemic assistance, because your job is not putting you at risk by wanting you to sit next to a person who recovered from COVID. 

Why is someone who has Covid even there?  If that's the case, report it to your local health dept. and they will take care of your employer.

You are contagious with covid for 10 days TOPS!!!

2 or 3 days before you develop symptoms you are pretty contagious

then 2 or 3 days after you have symptoms (if you get symptoms) you are pretty contagious

then another 4 or 5 days you are contagious but it's a lot harder to pass it to someone.

If they HAD covid MONTHS AGO = it does not impact your worksite.

Almost everyone who dies of covid is no longer contagious with covid.

Many don't even test positive any more.

Your supervisor is probably just really confused by your question, as the rest of us are.

Why do you need to move away from someone that had covid and recovered?

For at least 2 months and probably 4 months or more, I'd want to sit by them, because they are immune from getting it again. 

IF someone has been diagnosed with the COVID virus, he/she should be quarantined at home, not be at work.  Your supervisor should have sent him/her home.  I would go and get a COVID test and go from there.