Hey @Steven_Kristoffer_Am - Just to follow up here, I’ve also reported this to our product team. You’re right that we should prevent customers from having the ability to select the same sheet for multiple inputs and provide a message explaining why. Hopefully we can make improvements here in the near future.
As Brian mentioned, if you want the data from your two Facebook accounts to arrive at the same Google Sheet, place a Stack Tables step before the Send to Google Sheets step. This will vertically stack your two data sets into one so that your Google Sheet will receive one consolidated export.
Let us know if you need any other help setting this up!