If you just want the account to appear at the top of the Folder Pane, Tools/Account Actions, select the account in the left pane, then Account Actions, Set as Default. Further sorting options are possible with Manually sort folders.

Thank you, sfhowers. That would take care of part of the problem, but not the whole. I kept trying to add the "manually sort folders" add-on last night, but it just wouldn't download. I ended up deleting all my accounts below where I wanted my primary business account, and re- adding them. Had to do it twice, as the first time, it added the accounts without all my folders. But it eventually worked.

May I ask a related question? I ended up having to do this because I changed my p/w, and the only way I found to actually deal with a changed p/w was to delete and re-add the account. And the only way to add the account according to what I read in the help forums was to remove all my passwords. These two together caused a cascade of other problems.

There has to be an easy way to simply change a p/w within Thunderbird, and thus avoid the hours it took me to get this fixed last night. Do you happen to know of an easy way? Thanks!

When you change a password with the mail provider, or the authentication method, delete the old passwords or oauth tokens for the account from Options/Security/Passwords/Saved Passwords, restart TB, and enter the new password when prompted.

Manually sort folders does not work with Thunderbird 78.

Why is account sorting not a built-in feature? It is a very basic functionality...

Also changing the order of folders should be an integrated function I think.