It took me a while but I finally settled with an interface. Basically it’s a standard Master-Detail-Interface which tries to mimic the Apple Mail look. What you can’t see on the screenshot is a drawer that contains the interface elements to edit the transactions. I hid them in a drawer because you can also edit them directly in the table view. The drawer doesn’t fit in the overall design and I’m thinking about getting rid of it.

I’m pretty happy how this little project turns out. Although I’m spending a lot more time as intended, I’m learning a lot and this will hopefully help me with my next IC project.