I need animated box, so it looks like when jelly jiggles.
I need to export it to .dae (collada), so I would be able to add it to Xcode - SceneKit.
I tried everything I found, but I can not get the solution. I tried to animate it by simulating physics, but collada does not support that, so I tried to animate it with skeleton aswell, but blender collada export does not support skeletal skin animation, so that also does not work.
I would suggest you animate the "jiggle" box directly in SceneKit with the help of a shader modifier. No need to import a simple geometry.
See an example in this blog post: SceneKit Shaders Intro.