Feature requests should be submitted on UserVoice, this is the link for Drops related suggestions: https://twitch.uservoice.com/forums/310213-developers?category_id=389323
One option may be for you to define your own Reward ID for each reward, as documented here: Drops | Twitch Developers
With a custom reward id (rather than leaving it blank so it generates its own GUID), you could name each reward in way that would let you determine the campaign. For example campaign1-1234-56743-2425, and that Reward ID is returned in the Get Drops Entitlements endpoint as the benefit_id. The downside to this would be you would need to need each reward to be specific to a campaign and not using one reward in multiple campaigns.