CreateItemInBackpack( of_character, objtype, amount := 1 );
a new parameter like:
CreateItemInBackpack( of_character, objtype, amount := 1, NO_NOT_USE_STAK_IF_FOUND);
to order command to create new item and not to add ti prevous stack....
CreateItemInBackpack( of_character, objtype, amount := 1)
I know this is a bit screwy and takes a couple more cycles but
var item := CreateItemDescriptor(objtype);
item.CProps.NoStack := 1;
item := CreateItemInBackpack(of_character, item, amount := 1);
EraseObjProperty(item, "NoStack");
Just a note that CreateItemDescriptor is in POLSYS not UO.
CreateItemDescriptor was made for us to manipulate items before creation so we can create them straight into the stack instead of individually but of course this could be used the other way too
gotta love double-sided features 
var item := CreateItemDescriptor(objtype);
item.CProps.NoStack := 1;
item := CreateItemInBackpack(of_character, item, amount := 1);
EraseObjProperty(item, "NoStack");
Just a note that CreateItemDescriptor is in POLSYS not UO.
CreateItemDescriptor was made for us to manipulate items before creation so we can create them straight into the stack instead of individually but of course this could be used the other way too