Currently, the PlaySoundAction's 'Volume' and 'Source' Properties offer the ability to 'Create Resource' (which then applies it), and the ability to 'Apply Resource'.

However, what occurs is that whilst Resources can be created and saved from the PlaySoundAction's Property's value, they cannot be applied.

Repro Steps:

1) Open the StormKnight Sample from the GitHub InternalProjects repo.
2) With MainPage.xaml open, navigate to the Interactivity Panel, and select the EventTrigger applied to the Page.
3) In the EventTrigger's Properties Panel, identify, and expand the 'PlaySoundAction' Trigger.

4) Hover over the Volume Field, click on its 3-Dot Menu, and select 'Convert to Resource'
5) Pick a name for the Resource, and select any save location for it.

Observe how the Resource has been created, as seen by the Resources Tab being opened in the back, and now featuring a new 'Single' value.
Observe how the created Resource has not been applied to the PlaySoundAction's Volume Property.

6) Hover over the Volume Field, click on its 3-Dot Menu, and select 'Apply Resource'.
Observe how no results occur.

7) Repeat Steps 4) to 6), but for the PlaySoundAction's 'Source' field.

Observe the same unexpected results occurring.

Expected Results: If Resources can be created from the PlaySoundAction's 'Volume' and 'Source' Property values, that they can be created from any value in the field (and is automatically applied at creation).
Expected Results: If Resources can be applied to the PlaySoundAction's 'Volume' and 'Source' Property Values, the "Apply Resource" function prompts the user to select a resource to apply.
Expected Results: If this functionality is not supported, the options to create a Resource, and to Assign a Resource shouldn't be present in their 3-Dot Menus.