New to Salesforce. Wondering if anyone has been able to successfully use a quick text with a financial account merge field to get account numbers to populate in a task?

You can use a quick text with a financial account merge field to populate account numbers in a task. 

Please try the below steps

1. Go to Setup in Salesforce and search for "Quick Text" in the Quick Find box.
2. Click on "Quick Text" and create a new quick text by clicking on the "New" button.
3. Give your quick text a name and add your financial account merge field in the text area. You can use the merge field syntax of "{!Account.AccountNumber}" to insert the account number.
4. Save your quick text.
5. Now, create a new task and select the "Quick Text" option in the "Description" field.
6. Select the quick text you just created from the dropdown list.
7. The account number should now appear in the task description.