@Daniel Scott you would use this as a supplement to your regular Home Owners insurance policy, it is not meant to be the main policy for the property. 

It's designed to interface smoothly with Excel and Google Sheets, allowing you to easily export data for further detailed analysis or to supplement your current model.Considering your proficiency in real estate financial modeling, your feedback on its functionality could be invaluable.

We've spent the last ~2 years taking stock of our experience, supplementing our knowledge through bootcamps, research, and mentorship (thanks DeRosa Group Accelerator!)

With that said, since you obviously don't need supplemental cash-flow, how many more years do you have left on the mortgages?

If you do not have this you are at risk where if your property is damaged through natural disasters such as hail and tornado's, household issues like electrical fires, or vandalism in many if not most policies as well as liability issues.A umbrella policy is built to supplement your landlord policy. 

We are supplementing the occasional loss with gains from our other profitable Airbnbs.Not ideal!

Our financial goals are to supplement my and my 2 siblings’ incomes in the short term, and contribute to our retirement income in the long term.

No service is perfect.But when I ran the credit/background checks myself I could ‘read between the lines’ to get a pretty good picture of an applicant.Can’t do that with Cozy.Because of these limitations I'm considering using a different service, or supplementing with my own application.

Is it to supplement monthly income (cash flow), is it wealth accumulation, or a little of both?

We BRRRR 8-10 per year and the flips supplement and money left in the BRRRRs.We fund with a combination of Hard Money and Private Money.