As I recall, I read one that one of the proposals was to not restore unified Yugoslavia after the war. The fact is that Tito could not occupy the whole country and that without the entry of the Red Army in 1944, the state would be probably divided.
Here are some scenarios:
1) The success of Valkyrie extends the war in the east for a few months. That is why the Red Army doesn't enter Yugoslavia. Germany still lose the war, but post-war borders are somewhat different. The situation on the ground is that neither the Partisans, nor the Chetniks can control the whole country itself.
Western Yugoslavia is communist one, because of partisan support base. Communist Yugoslavia is made of Slovenia, Croatia and Bosnia and Herzegovina. Eastern one is Kingdom of Serbia with Montenegro and Macedonia. I don't know exact borders.
2) Somewhere in 1942., Wehrmacht at the moment of enlightenment realise that the Ustashas are liability rather than an asset. Hitler accepts one of Horstenau's proporsal and depose Pavelić and extreme Ustashas. New government is some type of military junta of Croatian Home Guard supported by Wehrmacht. Repulsion of Ustasha policy would diminish support for partisans, especially if new government reject Treaty of Rome and reclaim Dalmatia as integral part of Croatia. Tito will have hard time find new recruits. In one of German offensive, communists are destroyed and Tito is killed/captured.
After the capitulation of Italy, the Croatian government moves to the side of the Allies if the Allies promise their independence after the war. After a brief, but brutal war between the Croatian and German forces, the Anglo-American forces entered the territory of entire Yugoslavia and divided it into three parts: Slovenia, Croatia and Serbia. All three states are internationally recognized and they are NATO members. Slovenia and Croatia are republics, while Serbia remains monarchy.
3) No coup in 1941. Because of this, Kingdom of Yugoslavia stays a member of Axis., even government claims that country is ''neutral''. Red Army enters country and Stalin decides to divide Yugoslavia in few states. Those new democratic people's republics are loyal members of Warsaw pact.
4) Stalin invades Yugoslavia in 1948, resulting in crush of Tito and his resistance and divide country with permanent occupation in new republics. Yugoslavia is divided into 6 initial republics. There are no wars in 90s since Yugoslavia doesn't exist.