They are both artifacts of Gmail. I'd suggest you go to the Gmail website and disable the Important folder. And then in Thunderbird, select the account, right-click and de-select these folders in the Subscribe window.

Thank you, Zenos. I did as you suggested. Maybe you can also answer another question that I think may also have something to do with Gmail. When new messages are received in my Inbox, I cannot open them until a progress meter at the bottom of the screen completes. I don't know what progress is being measured by that meter. Might it have to do with the time it takes to put messages Gmail's All Mail folder? Seems odd. What is the value/purpose of the All Mail folder? Any thoughts on the identity/purpose of the progress meter would be helpful.

David

What is the value/purpose of the All Mail folder?

This is a Gmail thing and has got nothing to do with Thunderbird. https://support.google.com/mail/answer/82367

I don't know what progress is being measured by that meter.

I suppose that's the download progress for new messages. Perhaps you do have a slow Internet connection. Check the Activity Manager.

At the top right of the Thunderbird window, click the menu button > Activity Manager.

More reading here: https://support.mozilla.org/en-US/kb/thunderbird-and-gmail

There is also a link on that page to gmail's own support page. I'm not convinced that some of their recommendations are best practice. In particular, their spam filter persists in misclassifying some legitimate email messages, and it's not clear what one should do to fix this. You can go to the gmail website, login and mark them as "not spam", but a large part of my reason for using Thunderbird is to avoid those webmail sites.