We have an Origin System Variable @OPJ to handle this. According to this doc page:
It controls whether default to use the new file type (OPJU) when save the project and use the new file type (OGGU) when Copy Page to other software.
0 = Project to use new file type (OPJU) and copy graph page as new file type (OGGU)
1 = Project to use old file type (OPJ), but copy graph page as new file type(OGGU)
2 = Project to use new file type (OPJU), but copy graph page as old file type (OGG)
3 = Both will use old file type(OPJ & OGG)
To set the value you desire, Open the Command Window from the Window menu and type the following (substituting whatever value you want from above for n) and hit the Enter key. The value will be remembered from there:
Originlab Technical Support