Currently, there are a number of KeyTrigger keys that aren't registered or saved when selecting them from the listing of available keys from the dropdown menu.

I was able to find this with the 'Media' category of keys, but it could apply to other OS-hotkeys, such as the Browser-category ones, and potentially more.

Repro Steps:

1) Create a Studio Project featuring a MainPage.xaml
2) Introduce a TextBlock to the Page, rename it to a 'MyText', and set its Visibility to 'Hidden'.
3) Introduce a Button to the Page, and rename it to 'MyButton'

3) Navigate to the Interactivity/Triggers Panel, and create a new KeyTrigger on the PageRoot with:

Key: [A]
Modifiers: None
Fire On: KeyDown
Active on Focus: Unchecked
Conditions: None

Actions: ChangePropertyAction
Target: MyText
Property Name: Visibility
Value: Visible
Enabled: Checked

3) Navigate to the Interactivity/Triggers Panel, and create a new EventTrigger on the PageRoot with:

Source: <Self>
Event: Loaded
Conditions: None

Action: SetFocusAction
Target: MyButton
Engage: Checked
Enabled: Checked

4) Return to the KeyTrigger Trigger, and change the Key Property from [A] to 'MediaNextTrack'.

5) Click on the EventTrigger to deselect the KeyTrigger, then click on the KeyTrigger again.

Observe how the change to change the Key Property to 'MediaNextTrack' was not successfully logged or saved.

Expected Results: All available keys can be successfully written to the Trigger.