I haven't had luck with transparent materials exported as GLTF files from Blender.
But it's relatively easy to create a prefab in Unity that has transparent materials.
1. Create a new material in Unity.
2. Name the material (such as 'Glass') and set the rendering mode to "Transparent"
3. Lower the alpha value of the Albedo color to something closer to 0. (Zero will be completely transparent, while lower values such as 0.1 will still be slightly visible.)
4. Alter the value of smoothness to change the reflectiveness your material.
5. Import the model of the display case into Unity and add it to a blank scene.
5. Apply the new material to the display case portion of your model.
6. Make the display case with the glass material a prefab by dragging it from the Hierarchy into your Assets folder.
7. Right click on the new prefab and upload it to STYLY.
I'm trying to make a model of a museum-style display case. The top of the case needs to be a glass cube. How do I make a glass case that will show up as transparent in STYLY? When I export a GLTF model from Blender that has transparent materials, they show up as black.