CreoView API command to merge branch links

In some cases (I found that only with BIG models) when exporting Creo assembly to PVZ, it creates external structure files (separate pvs files) from top level subassemblies. I such case those branches are indicated with small blue/yellow arrows in icons of branch nodes in CreoView model tree. In CreoView UI there is a 'merge branch link' command that can be used to merge these kind of branches with main structure and get rid of the external pvs files. I have tried to find answer to two questions: 1 Why or in what case these external structure files are created? 2. is there a direct command or workaround in CreoView API to do the merge operation automaticaly without user interaction?