I’m very much a novice with Blender, but I enjoy figuring things out. I’m trying to create a floor tile with Texture and Displacement to import into another program. I’ve got all that to work in Blender but when I export it and view it in a 3D viewer. It has the texture, but no displacement. It’s completely smooth. What am I doing wrong? Is there a video tutorial out there that explains this process or could someone help. My import options for the other program I’m trying to bring the model into are STL, FBX and gITF. Thank you.
Welcome 
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Interchanging materials is not easy; every renderer does have different settings so the result might differ. This said: usually something like albedo, metallic, glossy, bump, normal and whatever maps to “transfer” but mostly the settings have to be “superwised”.
About what you did wrong: There is a bit too less info about this. You may have to double check Docs-Blender Manual: Addons → Import/Export → Scene gltf2 for needed or impossible settings. Or may show some screenschot about your sahder setop.
(Remember: blender can do screenshots Menu-> Window → Save Screenshot and be sure to show “the important part”. 
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Thank you. I think I stumbled on a solution. If I bring in the texture set from PolyHaven into the shader and remove the Displacement Node, but the add it back in thru the Add Modifier - Displace, then apply. That seems to work and the displacement stays with the model when you export it.
To add to this- displacement as a shader doesn’t export, but displacement as a modifier modifies the mesh, so it does