Do we have option to configure separate workflow for a particular Service or Category or Subcategory?

We can do this by going to setting page of process ‘workflow management’->‘Workflow’. You need to select specific Service in ‘Service’ and subcategory in ‘subcategory’ in the screen and then select a ‘group’ for which you what to give access and select ‘Present state’ and ‘Possible state’ and add the flow and save it.

Please refer our online help link for more details - Workflow