Got below email from VFS today :
You have booked a biometric appointment at the Canada Visa Application Centre.
If you are applying under the E/EP/F categories and have dependents who have the same application number as yours, you may now book an appointment request for them with the same application number using the biometric appointment web form.(https://vfs-cic.mioot.com/forms/appointments/).
Please make sure to upload the Biometrics Instruction Letter (BIL) of each applicant.
I got the same mail. However, you still cant make appointment on the website. I am going ahead with my appointment on monday. Will try booking another slot for my dependent, however not sure how the system will behave if I enter the same application number again.