Is There A Way To Dynamically Increase And Decrease Mass Energy?

[pittsburghjoe]

Would this hand us control of the spacetime fabric?

[GAHD]

Depends.
https://export.arxiv.org/ftp/arxiv/papers/1708/1708.07414.pdf

Fair amount of current models indicate mass is an effective result of the medium. This is one of the principles that leads to the idea of a higgs field. Some of the more edgy people go so far as to say spacetime itself is effectively a liquid-crystal-lattice of quark-antiquark pairs which results in mass-like behavior of matter via some similar mechanism.

Your question's a bit backwards if that apocryphal idea actually proves true; We'd need to influence spacetime itself to control mass.

[pittsburghjoe]

I'm all for modding the source code to the holographic fabric of spacetime, but I think we will figure out how trick mass energy levels first.