Itemized expenses under one receipt

[foxfriends]

Is your feature request related to a problem? Maybe it would be better as discussion? Please describe.

Most often when we have a bill to split, there's one receipt with many items (e.g. a dinner bill). Due to taxes/tips, the best way to import such a receipt would be as a single itemized expense, with taxes and tips spread equally across all items (or unequally, in the case of e.g. sin taxes on alcohol purchases that should only apply to some items). This way, we can then select who ordered which items (possibly splitting those individually for shared appetizers etc), and have the resulting price balancing without the user having to do any of the math themselves.

Describe the solution you'd like
I should be able to create an expense with multiple sub expenses, each with their own splitting strategies:

• Taken by 1 person whole (e.g. my main course)
• Split evenly by a subset/all people (e.g. shared appetizer)
• Split by shares, added to line items (e.g. tax/tip)
• Split by shares, added to certain line items only (e.g. extra alcohol tax)

Describe alternatives you've considered
Seems like the closest alternative right now is to include every item individually, and manually add the tip/tax amount on top of that, but this is greatly inconvenient.

A possible other simpler feature here might just be the option to input a price, followed by additional modifiers (e.g. +x% (tax) +x% (tip) -x% (discount)) to make inputting such an itemized as separate entries manually much easier and math-free.

App version
Live version (1.4.8?)

Additional context
I think this feature would also help significantly in making the #228 concept more reasonable: using OCR to extract the items, tips, and taxes from a receipt and creating an itemized representation of that receipt automatically would be HUGE.