My Gmail IMAP account has two trash folders. One is under the inbox, the other is a peer of the inbox just above [Gmail]. Neither has a trash icon (they're ordinary folders). No idea how I got in this configuration. The Gmail IMAP account in 68 is using maildir. The Gmail account in 60.8 is using mbox. 60.8 and 68 each have their own profile. I'm using view -> folders -> all.
Thunderbird 68.0 enables delete in the context menu for both those folders. However, when I try to delete them nothing happens. Thunderbird 60.8 will display a "Delete Folder" message box warning me that deleting this folder is not undoable ....." if I try to delete either Trash folder.
I expected 68.0 to act like 60.8 when I try to delete one of those Trash folders.
The FolderFlags add-on doesn't support version 68. Each version is using its own profile. I installed FolderFlags under 60.8 and used it to make the second Trash folder a Trash folder. The icon changed to become a trash folder. I then deleted the first trash folder, exited Thunderbird and start 68.0. No change - both Trash folders exist and neither has a Trash icon. File -> Compact Folders has no effect.
60.8 is using "just mark it as deleted. I thought I had made the same change for 68 but I was wrong. I changed it from when I delete a message: move it to trash to just mark it as deleted. I then tried deleting the first trash folder again. I got the delete folder message box. I exited and restarted and now there is just one trash folder. Its still a ordinary folder, but its position has moved from above [Gmail] to down under "sync issues".
I exited 68 and started 60.8. It has only one Trash folder, but its on the old position as a peer of the Inbox, just above [Gmail].
I deleted the second/last trash folder in my Gmail account using 68. I used file-> compact folders and file -> empty trash. Looking at the subscription window for that account it still lists a Trash folder under [Gmail]. Its marked as subscribed. I refreshed the subscription window - it's still there. But its not visible in the folder pane.
If I log into gmail webmail I see a Trash folder listed right after All Mail and the Spam folder and [Gmail/Trash] right after "categories". The subscription window apparently recognizes the latter as a folder but its not listed in the folder pane despite being subscribed.
There seem to be several problems.
I can't delete a folder in my Gmail IMAP account in 68.0 using "move it to this folder: Trash" because I can't get it to recognize a trash folder as a real trash folder. If the Folder Flags add-on supported 68 I might be able to workaround that. I can't fix the situation by temporarily using just mark it as deleted as several older bugs reports about not-visible Gmail trash folders suggested.
The Gmail IMAP account folders act differently under 60.8 and 68.0. The subscription window in 68 also claims there is a Trash folder that the folder pane refuses to display (despite it being subscribed)