Hello MM_SD,
Before that, can you please explain how exactly you are getting list of Tcodes in second screen? Which table you are hitting to get that list.
In ideal scenario, it should be something like, based on Authorization group you are getting list of tcodes to be displayed, so for new Plant-PO combination also, it should be via Authorization group.
In other words, there should be a different authorization group assigned to extra tcodes(which is not assigned to other tcodes) and new combination of Plant / PO should have this Authorization group.
Warm regards,.
Shyam