I have a work around for this that I am pretty proud of. Steps are as follows.
Make sure all your layouts have the same number of layers. Good practice anyway. Including a blank HUD layer.
Create a specific HUD layout, with the same number of layers.
Put the HUD elements on the HUD layer in the HUD layout.
Make them global.
I organise my game events in a single event sheet - so this is how i do the next step.
On load layout, I store the name of the current layout in a global variable.
Load the HUD layout.
In the HUD's event sheet (not the main event sheet), you have an On Level Loaded event which then loads the layout whose name you stashed in the global variable.
So basically, whichever layout you load, it immediately loads the HUD layout, which is all globals. And the HUD layout loads the original level back in. The global HUD is preserved. It works perfectly. :)