You are welcome.
After further check I can confirm that you can submit with an LOE alongside a proof that you ordered the documents to the competent authorities, just joint it to your LOE in the same pdf, you can find the information on CIC website/Covid updates.
Later after submission you can send your documents through IRCC webform
https://secure.cic.gc.ca/enquiries-renseignements/canada-case-cas-eng.aspx , you can upload documents later via your profile only in the case when they send you an additional documents request, if you receive one you will see a new placeholder appearing on your application, anyway send it as quick as you can through IRCC's webform.
Good luck.