I suggest to Upwork to add feature to add hours for a week or even month. So I can add at once how much hours I worked this week/month.
It is very easy if we agree on hours amount with client and I have not to go to Work Diary and add hours every day.
While it is not possible to add manual hours for a month, you can always add manual hours for the current week as long as it's allowed by the client. You will need to do it in your Work Diary though.