You don't need to send all the pages to amend. And you should be able to efile an amended return from the Desktop program.
First you need to update your original return with the filing status before you amend. For the Desktop program you have to check the filing status inside the program. Open your return and go up to menu item
File > Electronic Filing > Check Electronic Filing Status
Then save your return with the status. Go to File-Save. And then close and reopen the program for it to update.
BUT I've been seeing posts that the Desktop program isn't updating the filing status. There might be a problem with that. So that might be why it won't let you efile. It doesn't know the original efile was accepted.
