If you are using the KBART files of "Licensed/Available Journals" or "Licensed/Available eBooks" retrieved from the Holdings (KBART) section of the Librarian Portal, newly-launched Springer Nature titles will appear within a week. If your institution has set up KBART automation, they will appear in your discovery service a further 1-2 weeks after appearing on the Librarian Portal files.
If you are using the public KBART title lists page, or use a discovery service without KBART automation and manually select collections within the discovery service, new launches will appear after a month.