How can I view the tax forms before I finish my data entry and file the return?

You can see your Form 1040, but until you pay your TT fees you cannot see any of the other forms or schedules in online TT.  Only the desktop (CD/download) software has forms mode.

PREVIEW 1040

https://ttlc.intuit.com/questions/1901539-how-do-i-preview-my-turbotax-online-return-before-filing

Click on Tax Tools on the left side of the screen. Click on Tools. Click on View Tax Summary. Click on Preview my 1040 on the left side of the screen.

https://ttlc.intuit.com/community/printing/help/can-i-print-a-copy-of-my-turbotax-online-return-before-i-file-it/00/26244

You will need to pay the TurboTax account fees before you can view or print your complete tax return.

To pay the TurboTax online account fees by credit card, without completing the 2020 return at this time, click on Tax Tools on the left side of the online program screen. Then click on Print Center. Then click on Print, save or preview this year's return. On the next page, to pay by credit card, click Pay Now. The next screen will show a review of your Fees, click on Continue. Complete the next screen to pay by credit card and click Continue.

However, you can view your Form 1040 at any time. Click on Tax Tools on the left side of the screen. Click on Tools. Click on View Tax Summary. Click on Preview my 1040 on the left side of the screen.