Why can't I use the ENTER key instead of the TAB key to move between fields?

Are you new to Quicken for Windows?

Welcome.
Please read this for more information, some videos and a list of resources to help familiarize yourself with Quicken:
https://www.quicken.com/quicken-tips
https://www.quicken.com/complete-guide-getting-started-quicken-2018-windows

Quicken Help! (Quicken for Windows)

If you're unsure on how to do something, you can find more information about a specific task, function, feature or report in Quicken Help.
To access Quicken Help simply press the F1 key from anywhere in Quicken (or click Help in the Menu bar, then click Quicken Help).
Use the Contents tab to see the available books in Quicken Help. Click on one of the books to open it. Click on a chapter to drill down to more details.
Or use the Search tab to search using keywords, e.g., "buy security".
Some Quicken view screens may have a blue (or yellow) button with a question mark. Click it to get view - specific help.