I had an instructor ask me recently whether it was possible to create an assignment in the Grade Book via an Excel upload. I couldn't find an answer by searching the community, so I tested it out myself. I figured that I should share the results of my testing and the steps for anyone who might be interested.
This is probably best for an on-ground or hybrid course since the assignment is created in Canvas as a "no submission" assignment by default.
Export current gradebook
Add a column to your file
Add a title for the assignment and points possible in the appropriate fields
Input student grades for assignment (if you don't have grades available yet, type a space into the field; you'll get an error message if you don't put anything in the field)
Save your file as a .CSV
Import file into grade book (note: you will be prompted to confirm that you are creating a new assignment)