Years ago I wrote a post on reordering accounts in Thunderbird and recently found myself needing to do it again. Some of the instructions in the original post are now outdated, so here is the updated version with Windows 10 paths.
In Mozilla Thunderbird each time a new account is added it appears at the bottom of the mail list. I wanted to reorder accounts and move one to the top, but Thunderbird does not have a built in option to reorder accounts. The answer is to edit prefs.js file. On Windows 10 this is located at
Look for a line like:
This is the line you will need to modify to control ordering.