I'm trying to do something extremely janky and I'm wondering why there isn't any support to adding chances to the recipes included, as it seems like it could be useful outside of the extremely janky stuff I'm trying.

You can add chances, try right clicking on the product you want to add probability or ranges to.
Edit: The information tab on the mod page has an example screenshot as well.

I'll see if that works on my end and I'll report to you if it does; thanks for the heads up though! There's a chance I'm not right clicking the right place so I'll try again.
Edit: It is working; thank you!