To add or remove columns to the registerSelect "Account Actions"
Select "Register Columns..."
Or in newer versions you can click the gear icon in the upper right hand corner of the account register to get a list of available columns. Click to put a checkmark in the missing column(s). (Also explore the new columns, added to your version of Quicken, if they might be helpful for your needs.)
How to customize an Account Register in Windows
@JustBeingMe999 Wrong gear icon, check first screenshot.