Allow Maxiumum Session Time per User/Group
The current 'Maximum Session Timeout' is only available to be applied globally - this should be allowed to be configured / applied for different authentication methods, or as part of a Group Configuration. This is to allow RADIUS users a different session to a Local User.
It seems to me that this can already be done in UTM. You careate a Filter Action with desired categories are set to Quota, and a quota time limit, then assigning that Filter Action to appropriate user groups.
Asadul Hasan commented
In this case customer is looking to have custom Maximum Session Timeout for each user instead of applying the policy globally to all the users.
Authentication > Services > Global Settings > Maximum Session Timeout
This is applied Globally.