Importing transactions from my bank which are in CSV format into the check register into QB Desktop 2020 Pro. Is this possible?

You will need a 3rd party app to import or convert your bank statement.

Hello there, @Matt_Moore. 

I know you want to import bank transactions in a CSV format. Please know that you can only import your bank transactions using a .QBO file in QuickBooks Desktop. 

As Fiat Lux - ASIA mentioned, you can use a 3rd party app to import them, or convert your bank statement from CSV to a .QBO file. 

Once converted, you can follow the steps to import a .QBO file:

1. Select Bank Feeds from the Banking menu, then Import Web Connect Files.
2. Select the .QBO file you saved or converted, then select Open.
3. When asked to select your bank account, use a QuickBooks account that exists if the account you're importing transactions into is already set up in QuickBooks, or select Create a new QuickBooks account if the account you're importing transactions into isn't in QuickBooks yet. Learn how to create an account.
4. Click Continue, the select OK when you see a dialog box telling you that the data has been successfully read into QuickBooks.
5. Review your transactions in the Bank Feeds Center.

For more insights about bringing your bank transactions in to QuickBooks, you can visit this article: Set up or edit bank accounts for Bank Feeds in QuickBooks Desktop.

For future reference, you can check out this article to learn more about exporting, importing, and edit IIF files your lists and transactions in QBDT. 

We're always around here to guide you some more should you have additional concerns about importing your bank transactions. Take care!