Generally, if you have a variable that may not be used, you should proceed it with an underscore ( _ ). This bypasses the "unused_variable" error too. You also get the added bonus of it popping up first whenever the editor is showing options for autofill.
If you are having trouble, you can use:
export var temp = someCalc()
And then it will appear in the Inpsector as well.
However, whenever I need to see a variable during testing/building, I usually build my own debug function into an input somewhere. Something like:
And I'll fiddle with that until I know my code is doing what I want.