I actually think the best way IS to connect Venmo to the COA using online banking. While Venmo is a payment method, it's also very much a bank account.

Hear me out: Download transactions from your bank and from Venmo. Record the income and expenses as normal against the Venmo account, as if it it were a bank account. Payments made through Venmo but deducted from your bank would be recorded as transfers to your Venmo balance (simple by way of Rule), and since they are recorded on both the bank side and the Venmo side, they balance. Cashouts from Venmo to your bank are recorded as transfers to your bank. You do have to pick a good starting point in terms of your "opening balance" in Venmo, but other than that, it's pretty simple and--dare I say--kind of great. I'm sure some expert will tell me I'm wrong, but it's working for me!