How can I see which bosses I haven't beat with a specific weapon yet?

You get some special drops for beating a boss the first time with a particular weapon. Those are kinda useful, so I thought I might want to farm a few more of them. What I can't seem to find is a way to see which bosses I have beat with which weapon already.

Is there a way to figure out which weapon/boss combinations I haven't completed yet that will drop interesting loot?

I'm assuming you haven't unlocked the Pact of Punisment yet, because it has a nice interface that tells you which rewards you've earned with your current weapon. The Pact does unlock at certain point of normal gameplay, but I can see why it might take a while to get it open.
In Hell Mode, the Pact is available from the start.

It also does other things, but let's not go into those to avoid spoilers. The screenshot, from the Hades Wiki -page, is also cropped to avoid spoilers.

As for before then, to quote our good friend Skelly:

I don't know, there's always the invention of writing stuff down? You'll figure something out.