I used to be able to file more than one return with TurboTax, but using TT Live, it doesn't seem to give me that option. Need to file an extension for my brother. Tips?

I can always fill out the extension application on paper, but I've never done this and TT always does a great job of calculating net taxes owed, etc. Having already filed my own return for 2020,  TT doesn't even present any of this as an option.