How can I force Thunderbird to reload IMAP folder structure

In version 10.0.2 (current) and most recent versions:

Click on the account line in the folder tree (the line just above the Inbox)

You should get a screen of options, find Manage folder subscriptions and click on it

1. Click the Refresh button
2. Close the folder list window
3. Click the little triangle at the top level of the account in the folder tree to hide the folder list
4. Click it again to show the folder list

I've just confirmed that this works for me in 10.0.2

https://support.mozillamessaging.com/en-US/kb/thunderbird-and-gmail

I think in that website you can find more useful information about Gmail x Thunderbird. Also, I found out in other forum the following:

Thunderbird refreshes the folder list when it connects to the server, in particular, at startup. You can force a refresh of the folder list any time by collapsing and re-expanding it.

Collapsing and expanding the folder list for the whole account worked for me.

If you uncheck Tools » Account Settings » Settings » Advanced » Show only subscribed folders, it will display all folders.

That worked for me.