Can I use "Bank Rules" to categorize transactions that are manually entered into QuickBooks?

Welcome to the Community space, @hcoffin1. I understand how significant it is for you to categorize transactions using bank rules. Allow me to clear up any confusion here and help you understand more about this.

Bank rules will only apply to those transactions coming from the bank. That said, manually added transactions won't be included. 

To know more about how bank rules work, check out this article: Set up bank rules to categorize online banking in QuickBooks Online. 

Furthermore, here's an article that'll help you in reconciling an account in QuickBooks Online. 

 If you have additional bank transactions and any QuickBooks-related inquiries, drop them in the comments section. I'd be more than happy to assist you.