After you connect to a server for the first time, Horizon Client connects automatically to that server the next time you start Horizon Client.
To disable this feature, select the server shortcut on the Horizon Client Home window, press Control-click, and deselect the Always connect at launch setting.
If there are other server shortcuts on the Horizon Client Home window, you can enable the Always connect at launch setting for a different server. You can enable the Always connect at launch setting for only one server at a time.