How can I view and edit all capital gains transactions (cost and proceeds) at once without having to select each transaction individually and go through multiple screens?

You can view the results of your capital gains entries by previewing your return.

You can view your entire return or just your 1040 form before you e-file in TurboTax Online as follows:

1. Sign in to your TurboTax account
2. Open or continue your return
3. Select Tax Tools from the menu (if you don't see this, select the menu icon in the upper-left corner)
4. With the Tax Tools menu open, you can then:
   • Preview your entire return: Select Print Center and then Print, save or preview this year's return (you may be asked to register or pay first)
   • View only your 1040 form: Select Tools. Next, select View Tax Summary in the pop-up, then Preview my 1040 in the left menu

In order to edit transactions that were entered individually in TurboTax Online, you would need to revisit each transaction.