But it really doesn't address what this error means nor how it applies to my issue.
I've got a global boolean variable var_toggle which is defined:
Set( var_toggle, false ) = This formula has side effects and cannot be evaluated (Result when highlighted)
And it does this with load screen's OnVisible - once you are past that load screen you can't navigate back to it, so you can't hit that Set() again. When I insert a label with var_toggle in it's .text attribute, it gives me a result - false. The variable is also defined (false) in the File > Variables > Global section as well. Given the 'side effects' error it's a bit weird but the next part could be the real concern.
Then this variable goes on to define the visibility of objects on certain screens; pressing a button to makes the objects appear/disappear as such:
Switch( var_toggle, true, Set( var_toggle, false ), false, Set( var_toggle, true ) ) = This formula has side effects and cannot be evaluated (Result when highlighted)
So the initial declaration works fine even though it is said to have side effects BUT the button that switches between true and false doesn't work at all. This issue behaves exactly the same if I change the switch results to UpdateContext().
I am certain these are the only two place where this variable is Set/Updated. It is otherwise only used in object.visible. This method was working the other day and the only change I made was moving the initial Set() to the load screen.