Debug Diagnostic Tool - Can't modify rules - "failed to start dbgsvc getlasterror returns 0x0000422"

I was attempting to use Microsoft's Debug Diagnostic Tool (DebugDiag) to identity an Application Event Log error occurring in w3wp.exe / clr.dll, as described in this answer.

However, when I attempted to add my new Rule, I got an error dialog:

Cannot connect to service. Failed to start DbgSVC. GetLastError returns 0x00000422

How can I add the Rule successfully?

This error indicates that the Debug Diagnostic Service service is disabled.

To fix:

1. Start > Run > services.msc
2. In the Services dialog that appears, find "Debug Diagnostic Service" in the list.
3. Right-click that service > Properties.
4. Change the Startup Type from Disabled to Manual. Click OK.
5. Return to DebugDiag and try again to add (or modify or delete) the Rule.

DebugDiag will automatically start the service. The problem is that DebugDiag can't start the service when it's in Disabled state.