The only two options seem to be Upload and Export. Upload strips the design down to its non-functional elements. Export publishes the design in a format for 3D printing.
So why isn't a custom design accessible from other games?
Here's the immediate situation: I am playing two branches of a game, one where I accept a peace offer and the other where I go for the kill. In one branch I spent a lot of time designing two ships - one a new BB, the other a DN upgrade. They are available in that branch. They are nowhere to be seen in the other. Both branches have the same technology (as far as hips are concerned). So what gives?