If we knew how to create world simulation, and how to make it working 4D, then humans would be able to plug themselves in, and experience 4D space. Alternatively there could simulated 4D beings, whose sentience could be transferred to robot body in our real 3D space.
Fyi, string theory, which is a popular, well known theory that assumes 11 dimensions, doesn’t really have that much appeal in the scientific community. It’s still fun to talk about tho