I've asked a designer to work on my sample libraries UI, he'd like to try out the current version but he's on a limited internet connection and would prefer not to have to download all of the samples in order to play with the interface. Is there a way to make mini HR files so he can access the interface?

If he should just create the graphics, you could create a basic graphic elements and send him the Images folder and the screenshots, so he can work creating all the stuff using the same sizes. For my synth, the designer is creating the graphic elements just on the Image folders that I sent to him and it's working fine.