In Gaia 1 there was a way to import terrain from other heightmap sources such as into Gaia for stamping. In Gaia 1, the stamper required a special stamp format to work for technical reasons. In Gaia 2 / Pro, the stamper will work with any image file that unity supports. That means you can just import the heightmap images directly into unity without going via the scanner, and then use them in an image mask in the stamper. The only thing you need to be aware of is some import settings for the image to get the best quality for your stamp result.

Instructions for

1. Download a heightmap from as usual
2. Place the file(s) you want to use in your asset hierarchy.
3. Select the files in the asset hierarchy, and set up your texture import settings as follows:

4. Select the texture in an image mask in the stamper, either via drag and drop, or via the small circular file picker icon next to the Mask Image slot

The same principle should work for heightmap information from other sources as well, just make sure to apply the same import settings as shown above in step 3 to the texture / image.

BONUS: Note that you can create your own folder in Gaia\Stamps, and the stamp browser will pick this folder up and display its contents, so you can organize your stamps this way: