[BreakfastB0b]

I have a Physics degree for what it's worth. Though I'll admit I didn't articulate what I meant clearly.

The electron example was assuming that the increasing magnetic field was part of this hypothetical toy universe that violates time translation symmetry. Obviously constructing such experiment in our universe it's not surprising that the electron gains energy because as you said, it's not an isolated system. When considering the system generating the magnetic field it becomes obvious that the overall system does not gain energy.

However our actual universe, at the galactic scale, is just like the toy example. New Space / Energy is created out of nothing as the universe's expansion accelerates. There is no paradox here because conservation of energy is not fundamental but emergent from symmetries via Noether's theorem. Space is a "material" that is not "diluted" by expansion and contains energy.

The inflaton field at the heart of hyperinflation / big bang theory also expands without dilution.

Perhaps there is some larger system our universe is embedded in that does respect time translation system / conservation of energy and the expansion is being driven by a larger process loosing energy but we can't observe it.