I have contacted CIC and below is their reply.
Good day XXXXXXXX,
Thank you for contacting Immigration, Refugees and Citizenship Canada (IRCC).
We verified the information that you have provided and can confirm that at this time, it is not possible to link your application to
your new account since your application is still waiting to be processed. Please visit our
website in order to determine when we will begin to process your application.
For information purposes, you may at some point receive an email notifying you that
Your application (X000000000) has been updated. You should be able to link your application at that time.