Anyway to change the posting period on a voiding journal? I get the error 'The G/L impact of a voided transaction cannot be changed.' The period I am attempting to move the void to is open

You said the period you are trying to move it "to" is open, but what about the period "from" ?

Both are open, trying to set back to one period where the voided transaction is posted to

Pretty sure this can't be done - maybe try changing the void date on the original transaction?

Yeah seem it isn't possible. The voided date has been set back and does not make an impact, I will just create manual JE's, messing with voided transactions can open a real can of worms...