What

When a custom Navigation Overlay is selected, the Navigation block should hide the controls that allow setting the Overlay background for the default overlay. These controls are specific to the default overlay and should not be exposed when a custom Overlay is in use.

Why

Custom Overlays are designed to define their own appearance entirely within the Overlay template. Showing background controls for the default overlay when a custom Overlay is selected introduces confusion about which layer is responsible for styling and suggests behaviour that will not apply. Hiding these controls reinforces a clear, intentional editing model and avoids misleading configuration options.

How

Conditionally hide Overlay background–related controls on the Navigation block when a custom Overlay is selected.

• When the default Overlay is active, existing Overlay background controls remain visible and unchanged.
• When a custom Overlay is selected, Overlay background controls are hidden.
• No additional messaging or alternative styling controls are introduced as part of this change.

⚠️ Note this PR which splits the current Overlay and Submenu control into dedicated controls #73824

User Stories

The following stories capture the intended outcomes from a user perspective:

As a user, I want Overlay background controls to be hidden when I’m using a custom Overlay, so I’m not presented with options that don’t apply.

As a user, I want the editor to only show controls that are relevant to my current Overlay type (custom vs default), so the interface feels clear and predictable.

As a user, I want to be confident that any background styling for a custom Overlay happens inside the Overlay template, not on the Navigation block.