Steps to download and install offline zip package of a tool into Launcher:

1) Download a tool zip file from https://itools.infineon.com/stable/offline_packages/
2) Copy downloaded zip file path (including zip file name)
3) Open Toolbox Launcher, go to configuration menu and paste copied zip file path in Update site input box and click on Ok
4) You should be able to see Install/Update button of downloaded tool in Manage tools section and click on to proceed with Installation of tool update.
5) Reset the Update site configuration afterwards