Is there a way to split a transaction by % and then make it a rule?

There's definitely a way to do that, mattoconnorlel-a.

You can create a bank rule to automatically categorize, split, and prefill some information when transactions are downloaded from the bank. I'll show you how to do it:

1. Select Banking from the sidebar menu, then go to the Rules tab.
2. Click the New Rule button.
3. From the For drop-down menu, select Money in or Money out.
4. From the In drop-down menu, choose a bank or credit card account.
5. Set the rule conditions. Decide the transaction must meet All or Any of the conditions.
6. In the Conditions fields, specify whether the rule applies to Bank text, Description, or Amount. Then, select Contains, Doesn't contain, or Is exactly to decide when how Quickbooks applies the rules.
7. Go to the Then assign section, select the appropriate transaction type from the drop-down menu.
8. Click the Add a split link, then select Percentage from the Split by drop-down menu and enter "75%" and "25%" in the Percentage fields.
9. Set the appropriate categories and enter the necessary information.
10. When you're done, click Save.

With QuickBooks Online, you can also turn on the Auto-add feature to your bank rules to automatically accept specific transactions into your books. All the steps and processes are discussed in this article: Set up bank rules to categorize online banking transactions.

I also recommend reading this guide to help you control, customize, and automate how QuickBooks categorizes transactions if a match is not found so you can save time on data entry: Tips for Working in QuickBooks Online’s Bank Feed: Managing Bank Rules.

Fill me in if you have any bank-related questions or concerns. It's always my pleasure to help.