I have a need to logout certain rdp sessions (superadmin account) after 15 minutes of inactivity. if someone forgets to disconnect a session from one of the windows servers and a password changes overnight, it wont lock the account. I have found a group policy setting for this (end a disconnected session in remote desktop services) but i only want to apply it to the super admin account, is this possible by just adding the super admin to the gp permission.
You describe the condition as if someone forgets to disconnect a session and you are applying End a disconnected session setting on your Remote Desktop Services Sessions. First you need to understand the difference between two settings:
It sounds like you need the latter, instead.
Both of these setting can be set in Computer Configuration or User Configuration. As you want to apply this only on specific user(s), you need to use the settings on User Configuration > Policies > Administrative Templates > Windows Components > Remote Desktop Services > Remote Desktop Session Host > Session Time Limits.
As always, you can apply a GPO only to specific users if they are on a separate OU container.