I want to have two Firefox accounts. One for Work and one for home. On my account I was using one of my home email accounts as a primary and another home email as a secondary. I added my work email address and and made it the primary and removed my home address that was the original primary for this account. Can I now start a new account with that home email or will it not be available to use since it was once a primary for the other account?
This may not be the answer you want to hear, but go ahead and try. I don't see any reason why it wouldn't work. I have shuffled many accounts with Firefox over the last dozen or so years.
You can also set up numerous Firefox profiles and then just sign into each account on that specific browser profile. If you need help with setting up Firefox profiles and creating custom short cuts/launchers in Windows or Linux, I can give you the links for clear and easy to do instructions.