Runtime API in Unreal

Can I use the Sloyd API to add objects at runtime?

Yes you can! Check out this example:

How to import meshes at runtime?

For now, you'll need to use a third party plug-in to enable runtime import of 3D objects, called glTFRuntime.

You can buy it on the Unreal Marketplace, or you can download it for free on Github:

GitHub - rdeioris/glTFRuntime: Unreal Engine Plugin for loading glTF files at runtimeGitHub