libreCMC/package/luci/applications/luci-app-shellinabox/luasrc/controller/shellinabox.lua

module("luci.controller.shellinabox", package.seeall)  --notice that new_tab is the name of the file new_tab.lua
 function index()
     entry({"admin", "system", "tab_from_view"}, template("shellinabox/view_tab"), "Terminal", 2)  --this adds the second sub-tab that is located in <luci-path>/luci-myapplication/view/myapp-mymodule and the file is called view_tab.htm, also set to the second position
end