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If you just took a homogeneous gas or material with a high density and encased a localized region of spacetime, then leave a void in the middle, you should essentially have a region of negative curvature when compared to the shell.
Assuming spherical symmetry to this setup, then the space-time geometry of the void will be flat (described exactly by special relativity), and the region outside it will obey the Schwarzschild metric. Unfortunately, no part of this looks like a wormhole metric. Otherwise we could build wormholes quite easily.
To make a wormhole, the popular description is to connect the singularities of two Schwarzschild metrics to each other (how to achieve that
is an exercise left for the forum). But this connection is violently unstable. It requires something which is gravitationally repulsive to keep it open, which means a negative energy density in a manner which violates the energy conditions -- and this is very likely an unphysical solution to the equations.
Another form of wormhole that can appear in the mathematics is for a charged or rotating black hole. Either effect (or both) generates a region of space-time where space flows back outwards -- into a new universe, perhaps. However, there are again clues that such solutions are unphysical.
There's nothing inherently wrong about putting wormholes in SE -- the mathematics describing such a thing exists. It's just a question of programming feasibility and one's stance on including speculative / sci-fi realms of physics. Alcubierre drives are already in Space Engine and those are just as unphysical as wormholes.