How do I recover the trash mailbox in the mail application

G-Mail is IMAP isn't it? Therefore, it should not be hard to remotely remove folders.

I"d be curious if you could log into web-mail and let me know what you see there. If it's still missing, just CREATE a new trashfolder in web-mail. And that SHOULD fix it.

But it' late here and I may be reading this whole situation wrong.

Open your local Library. It's hidden so in Finder, hold down Option key and in the top menu, under "Go" select Library. The Finder will open your local library.

Enter Gmail in the search box and you should find a folder named,

[Gmail].mbox

Don't ask me why the name is written that way. 😁

Right-click the file and select "Open Enclosing Folder" and you will see all your mail boxes for gmail. If the Trash is there, you have not deleted it.

Now, what you need is for someone to tell you how to put it back into the mail app.

I do not know how to do that, but at least you know whether or not the Trash is still on your system.

If you are using TM, it is much easier. Just open the email window and then open the TM interface from the Launch bar. You will see all your mail for as long as you have been using TM. Find the first instance of the Gmail trash in the time windows and click on it to select it. Not click the little Gear in the TM window and select restore it. The trash will be restored to your gmail account.

I have done this once and it works.

From the Mail menu bar, select Mailbox > New Mailbox... and create a mailbox named "Trash" (or whatever it was called before.) Select the new mailbox in the Mail window, then select Mailbox > Use This Mailbox For... > Trash.