mail app won't create mailbox

I created a new mail box under "On my mac" named "undisclosed". When I tried to create another mailbox, "2017" beneath "undisclosed" the location was given as "On my mac". When i scrolled down "On my mac", "undisclosed" was not there. However if i exited from creating a new mailbox, it was in the list on my mac. I was able to create sub mailboxes under other already existing mailboxes.I deleted the new mailbox and re created it, quit mail and rebooted, didn't help, still couldn't create a new mailbox beneath "undisclosed"

I am running Sierra on an iMac using gmail with apple mail utility

If you are trying to create a new Google Mail Box that is achieved by clicking the plus sign to the right of the Google Mailbox list, then you get the dialogue box pictured below. If you want a "Local" Mailbox that is achieved by clicking the plus sign to the right of the Mailboxes list at the top.
PS. The Plus sign does not appear until you hover over the spot to the right of the heading.

thanks but I am working with the apple mail utility not on the google mail site

This is the Apple Mail "utilility" as you refer to it. It is not a utility but an Application and it's called simply Mail or the Mail app. What I have posted is a picture of my Mail app with the mailboxes listed in the sidebar. As stated, to create a local mailbox (on your Mac) the same method is used. " If you want a "Local" Mailbox that is achieved by clicking the plus sign to the right of the Mailboxes list at the top."

Thanks; I found the + sign and created the mailbox I wanted, "undisclosed". However when I used the + to add a new mail box beneath "undisclosed" and scrolled down the sidebar list of existing mailboxes, "undisclosed" did not appear, but another old (deleted) mail box with a name beginning with the letter "u" appeared. If i exit the New Mailbox window then undisclosed appears in the sidebar, and the old deleted mailbox does not. I am scratching my head.

Continue to have trouble creating mailboxes. Using the + symbol opens up the menu of existing mailboxes but does not include a new mailbox that I just created so I can't add a mailbox under the new one. I am not having any trouble otherwise on my Mac, only bad behavior in the mail app. Also I had a dozen mailboxes for 2016 one per month, with saved emails in them. The mailboxes are still there but al the emails have disappeared.

Have you read and followed Apple's directions here:
https://support.apple.com/kb/PH22314?locale=en_US&viewlocale=en_US
and here:
https://support.apple.com/kb/PH22315?viewlocale=en_MK&locale=en_MK

or here:
https://www.lifewire.com/organize-apple-mail-with-mailboxes-2260022

I will admit that Apple's Mail.app can do some odd things at times, but your problems seem to be rather extreme. But not sure if it's fully at fault here or not.




- Patrick
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When you get to the point of "undisclosed" then right click on it. Then you will get a pull down and the first item is "New Mailbox" whatever you name it, it will be under "undisclosed".

Alternatively, as in @Rod Sprague's post, do you see the up-arrow, down arrow next to the "Google", click on it and select "undisclosed" then type in the name of the folder you want.

Yet another alternative, if all else fails, open up Gmail in Chrome (or any other browser) and enter in gmail.com into the unbar (or URL) and then enter. You'll get a generic login, and use your Gmail login. Then log in. Add the sub-folder from there.