How to hide the workflow models for certain groups or a user in AEM 6.5?

Question:

Any Idea How to hide the workflow models for certain groups or a user in AEM 6.5?
runtime workflows are updated in /var/workflow/models,
In useradmin console I am unable to set permission to specific workflow model because workflowmodel is in /var/workflow/model is xml file and NOT having
mixnTypes: rep:AccessContrallable property.
Adding the system tag to workflowmodel hides the workflow model for all users but to specific group

my use case is I want hide workflow name in the dropdown option in start workflow when specific group members trigger workflow

Solution:

1. creating custom workflow under /conf/global/setting/workflow/model/projectname/workflowmodel(projectname is sling:folder with mixinType: rep:AccessControllable

2. create workflow model above folder and sync

3. created runtime workflow under /var/workflow/model/projectname/workflowmodel

4. goto useradmin console update permission specific group(allow/deny) to workflowmodel in /var/workflow/model/projectname/workflowmodel