I want to make sure some changes I made to various leveled lists are working...is there a good way to test this?

Uh, ingame would seem the most easy method. I'm not sure how else you could. Perhaps you could make a room with loads of different leveled lists behind a fence and see what they come out as. Cant claim to be very experienced at this though so I don't really know.

There's a small button in the bottom "Preview calculated result". Enter the player level and click it.