Hi Balram.Deswal,
You can implement this customization by placing the following files in nx_root/site/mods/magic. Let me know if you have any questions.
This trigger will fire when WEB_TOOLBAR_TAB is changing and replace the new value with 0.
preferences.mod
MODIFY USP_PREFERENCES POST_VALIDATE zSetTab() 10000 FILTER(WEB_TOOLBAR_TAB {} && EVENT("INSERT UPDATE"));
preferences.spl
USP_PREFERENCES::zSetTab(...)
{
string method;
method ="USP_PREFERENCES::zSetTab";
logf(MILESTONE, "%s started", method);
uuid who;
send_wait(0,top_object(), "call_attr", "cnt", "current_user_id");
who=msg[0];
send_wait(0, top_object(), "call_attr", "api", "update_object_super", who, persistent_id, 0, "WEB_TOOLBAR_TAB", 0);
logf(MILESTONE, "%s ended", method);
}