If you have the get message blue button like I show in my image, use the three dots to expand the menu to select the other available modes. I use "all folders"

Hi Matt. I am using Win 7,and my TB controls look different from what you sent,although I can select folders,that still doesn't show all of them.

Are the missing folders not subscribed? For IMAP accounts, right-click the account in the Folder Pane, Subscribe, Refresh, subscribe a folder by checking the box.

I don't see any subscribe option. I can find the content I want with the search function,so I can live without the folders all being visible in the left pane. It is a problem going back years. I will leave the matter as it is. Thanks.

Subscribe is only for IMAP accounts. Try this: Help/Troubleshooting Info, Profile Folder, Open Folder, close TB, delete folderTree.json and open the subfolder of Mail with your account files, e.g. Mail/pop.mail.yahoo.com. Do you see files with no extension, named after the missing folders? If so, delete the like-named .msf files, restart TB, and see if the folders now appear in the Folder Pane.