KGB - as You mentioned, some stamps from post-Yugoslavia period are not listed in Scott.
You are correct, as Scott have his own policy what to list or not, and one sample is REPUBLIKA SRPSKA KRAJINA, short lived independent country, that made independence proclamation as result of destruction of Yugoslavia.
Scott refused to list this territory, by explanation that they have no enough proof, that this territory have own postal system installed.
But other, major catalog, as Michel, have it fully listed and very well covered.
