Group Topics is used to manage Gnus groups.

For example, you can,

Place groups (mail folders) from Gmail into "gmail" topic

Place groups (mails folders) from Outlook.com into "hotmail" topic

Make "gmail" and "hotmail" belong to the root topic "Gnus"

Enable it is just one line,

(add-hook 'gnus-group-mode-hook 'gnus-topic-mode)

Now comes the question how to delete/add/move the topics?

The official answer is to read its manual.

But there is a simpler solution. All you need to do is insert below code into ~/.emacs or ~/.gnus.el,

(with-eval-after-load 'gnus-topic (setq gnus-topic-topology '(("Gnus" visible) (("hotmail" visible nil nil)) (("gmail" visible nil nil)))) (setq gnus-topic-alist '(("hotmail" ; the key of topic "nnimap+hotmail:Inbox" "nnimap+hotmail:Drafts" "nnimap+hotmail:Sent" "nnimap+hotmail:Junk" "nnimap+hotmail:Deleted") ("gmail" ; the key of topic "INBOX" "[Gmail]/Sent Mail" "[Gmail]/Trash" "Drafts") ("Gnus"))))

The management of topics is as easy as editing above code.

My setup always works no matter ~/.newsrc.eld is loaded or not.

BTW, "hotmail" and "gmail" are the keys you used when configuring IMAP accounts,