Just filled in the form to figure out if one could submit the PCR-test later on, but that does not seem likely. After all the seven pages of data was filled in I got a reference number and the status of my application. There is no "Add test result"-button there. Guess I will have to wait until I have the test result two days before the travel.
How does one get the PCR test result in time to upload and submit the travel application within 48 hours of travel? Test results from the labs I can find take several days at least. Couple that with labs being closed for Thanksgiving and weekends, and we have an impossible situation.