Hi Daniel!
That’s an awesome explanation of the situations where you’ll run into this issue & the difficulties it causes!
I’m a big fan of using Monzo.me for bill splitting too but it is a bit of a pain that the repayments aren’t deducted from the monthly spend & Targets.
The team are aware of this problem & working to fix it. In the meantime, I’ve shared some (imperfect) workarounds at the top of this post.
I’ve moved your post here to keep all of the discussion about this idea in one place.