It should be there, in Local Folders > Outbox, but you said you already saw that, so not sure I understand the question… Is it that the message doesn't show up in Outbox?

Clarification: I see NO "outbox."

Ahh… I understand now, was a typo, you meant "no" but typed "now", LOL.

OK. You should look for Outbox in Local Folders as I indicated in my previous reply, near the bottom of the folder pane, below all your mail accounts. Your screenshot seems to indicate you were looking for it within the mail account.

The current problem is I no longer see the Local Folders!

Open *all* the closed roots (all those prefixed with >) and take a look inside them to see if you've accidentally click-dragged it into one of them.

Nope. Do not see it in any of them!

I can't see that you've stated whether the email clients are IMAP or POP3 or which OS you're running so, if you're running Windows 10 or higher, go to: C:\Users\[Users]\AppData\Roaming\Thunderbird\Profiles\XXXX.default-release then Mail or IMapMail depending on your set up and see if there is a 'Local Folders' folder. Are there files in here? Specifically, are there two 'Unsent Messages' files?

The Mail folder would still be present, and that's where Local Folders should be within the profile folder, even if the accounts are IMAP, because that's where Thunderbird puts all the mail stored locally on the computer.

In the menu bar, choose View > Folders > Folder Pane Header if not already ticked, to make that visible. Then, click on the '···' button to the right of the '+ New Message' button in that pane to display a list of options. One of the options available there near the bottom should be Hide Local Folders, which you have probably ticked, select it to untick it and make the Local Folders appear in the folder pane.

The following article shows the Folder Pane Header and explains the options available there:

https://support.mozilla.org/kb/new-thunderbird-115-supernova#w_look-and-feel-improvements-new-message-button-get-messages-folder-pane-options-meatball-menu