How do I set up a rule to mark all transactions in a given connected bank account as business transactions?

Good day, @louis-hortusdesi.

Let me help you create and use rules to quickly categorize your recent and past transactions in QuicKBook Self-Employed (QBSE).

If your downloaded transactions are usually the same, then you can create bank rules so QBSE automatically categorizes them for you. Here's how:

1. Go to Settings and select Rules.
2. Click Create Rule.
3. In the Description field, enter the customer or vendor you want to create the rule for. Select to check the Match exactly checkbox if you want QuickBooks to only use the rule when transactions match exactly.
4. From the Account drop-down menu, select the account you want transactions to go into.
5. Select Business from the Type drop-down list.
6. If you want QuickBooks to categorize transactions, click the Category link and choose a category.
7. If you want the rule to apply to transactions you've already categorized, select to check the Also apply to past transactions checkbox.
8. When you're done, click Save.

In case you're using an iOs or Android device, follow the steps in this article instead: Create rules to speed up reviews in QBSE.

If you have downloaded transactions that don't apply to the rules, you can manually categorise them. This way, you can organise your income and expenses. 

That should do it. If you have further questions in handling your banking transactions, feel free to post again to this thread. I'll be more than happy to assist you.