Resolution:
You need to distinguish by ServiceTypeName in the ds.config file. For example:

MoSesService-1
MoSesService-5
MoSesService-8

Once you have a similar configuration, you can follow these steps:

• You need to duplicate the MoSesService into MoSesService-? (from above example)
• Modify each service to set the Priority
• Update accordingly the ds.config file use by the user installation

An alternative way to set the priority would be as follows:

• Adding EnableMoSesPriority set to true in the ds.config file. And the code is supposed to convert Moses jobs priority (0 to 7) mapped into  GridServer priority (0 is 5, 1 =1, 2 = 2 , 3=3, 4 is 5, 5 is 7, 6 = 8 and 7 is 9)

There are no UI controls for setting priorities.