Loan Payment Tracking via API

SKN

I am a developer and run multiple businesses on Wave. Part of what I keep track of are monthly payments, principal, and interest on loans, both when I am a borrower and a lender. I have been able to set this up manually using Recurring Invoices and Bills, but it requires a lot of manual math and editing each month to get the amounts correct. I started looking into the API today with the intent on building something that could automatically calculate and create the monthly Bills and Invoices with the correct Principal and Interest due. A few questions I'll need answered to make this work:

• I see where it is possible to create or clone an invoice, but not update an existing one. Is that possible?
• I see an Object defined for Estimates but not Bills, and no way to work with either. Are either supported yet?
• Is there any support for hosting UI components inside Wave, to setup a loan for example, or would I need to use my own web server? If I get this working I'd like a way to share with the Wave community.
• I'm a bit confused on how to properly get started with the API. I'm very familiar with OAuth and Bearer tokens. I see the screen where it wants me to create a new Application - is that the proper first step, even just to get API access to my own businesses?

Last, in case I'm overthinking this, is there any existing Integration or Zap that can do this already?

Thanks.

SKN

I did just find this topic, so it looks like Bills may not be coming anytime soon.
https://community.waveapps.com/discussion/9921/bill-api

Maybe a shorter term workaround would be to allow the API to put "Buy this" products onto Estimates or Invoices instead of only Bills? Effectively they do the same thing - post a Transaction to a customer with charges to specific Income or Expense accounts.