Check your interface manual for what the “balanced standard line inputs on the back of the 4i4” actually are, they may well be combination inputs perfectly happy with unbalanced inputs too. Then there should be no problem. I don’t think you’ll damage anything either way, so try it and see.
Ideally you want to go to an input designed for unbalanced instrument level signals, that you can boost to line level (the Super 6 level can be quite low for a modern synth). That means separate DI, DI input on a mic pre, or a mixing desk/interface instrument or line input, with gain.