Do you mean like eg Dorian, Phrygian...? You can create these kinds of custom scales by hacking the presets. Here's a Dorian one. You should be able to drop that file into eg the Lead Presets folder; under Windows that's probably:
If you load a Song from the browser, then load that Dorian preset, you should find that your lead has been tuned to a Dorian scale.
You can't transpose these custom scales however; if you change the tuning they'll revert to the standard type.
It's not ideal but you might find it a helpful workaround until Artiphon provide more scales. The method for creating these custom tuning presets is described at the bottom of this thread: