To adjust the dimming levels of devices within a Scene you will need to be logged into your application and navigate to the Main Menu:
Then select options to the Scene associated with the Device you would like to dim(Circled in Red Picture 1), then select the Edit Icon(Circled in Red Picture 2):
Next, select the Scene Members Icon (In the bottom menu):
Now you will see the devices within the scene, Select the device you wish to modify to access its customization settings.
Once selected you should see the Dim Slide bar to adjust the dimming of the device. Click back arrow and then Save to save.