I use Thunderbird’s unified inbox as it is a very convenient way to manage multiple accounts. Yet there was a management account where the inbox was a huge pile of messages that needed to stay there but that I didn’t want to show in there unless I specifically clicked on that account.

No other guide on the first page of google results gave info on it, but here’s how you do it.

Right-click on the Inbox master node under which all the accounts’ inboxes are listed, then click on Properties, then Choose the selected folders to search, and un-check the Inbox of the account you want to hide. Then click on Update.

There you go.