Please add this to my bt account

That is the solution

I can't tell if you actually solved your problem or not. Normally, all your accounts will be shown in the left-hand Folders pane. If that's not what you were looking for, you may be interested in Thunderbird's "Unified Folders" feature. This article described it: https://support.mozilla.org/en-US/kb/switching-folder-pane-view