This refers to Moodle 34 from September 2018 3.6 from July 2019 onward.
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In a nutshell, the steps are:
1) Download and Unzip Step 1. Download files from Moodle assignment. Unzip. Keep the files in a specific folder.
Step 2. ) Use Track Changes in Word or a PDF annotator or similar to add your feedback to the filessubmissions.
Step 3. ) Zip the marked files back into a .zip folder.
Step 4. ) Upload the new .zip folder to Moodle.
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From the With selected… dropdown menu select Lock submissions and then press Go.
A pop-up message will appear asking if you want to lock all selected submissions. Press OK.
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Scroll back up. Towards the top left click on the dropdown menu called Grading action and select
Download all submissions.
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Note: If Groups mode in the assignment settings has been set to Separate groups. 
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Unzip the folder: extract the files. Move them to an area in your file folders named for your assignment.
Right-click on the folder and select Extract All.
A folder is present for each student.
Add your feedback files into the relevant folder for the student. They can be in any format and any number of files.
Go back to your Moodle site and from the Grading action drop-down menu again select Download grading worksheet. A .csv file will download to your computer.
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Now that you have downloaded all the submissions and the offline grading worksheet, it is time to mark and provide feedback. Open the folder that contain the submissions and you will see that the students who had submitted have their own folders created.
Important: please do not change the naming convention of these folders as this is what Moodle uses to ensure the feedback files are provided to the correct student.
A folder is present for each student.
Go into one of the folders and open the submission. You may wish to add any comments using the Word and PDF commenting tool, or by whatever mechanism you wish to use (by direct annotation using the Android tablets/Surface Pros - see how to annotate on Word using a Surface Pro).
You can also add other documents in the folder, for example a marksheet.
Add your feedback files into the relevant folder for the student. They can be in any format and any number of files.
When you are ready to save the document(s) save back to the student’s folder.
Once you have annotated the assignment or completed any feedback documentation for an individual student, you may wish to enter the mark for the student in the CSV file.
Open the CSV file you previously downloaded; you will see a list of students who are on the module.
In column G of the CSV file called Grade you can enter the marks for the students. You can do this all in one go or spread it out over time as long as you save the CSV to your computer.
For large cohorts you may wish to use the sort data in Excel to help manage the marks and submissions. To do this click on the Sort & Filter button in Excel.
A new page will load which lists what changes you’re intending to make. Click the Confirm button.
The student information table will appear. Scroll to the right and within the Feedback files column you will see the feedback documents have been uploaded to the correct students.
Another new page will be loaded which confirms what has been changed. Click the Continue button.
When you have completed adding in all marks on the CSV file click on the dropdown menu in the top left once more but this time select Upload grading worksheet. 
A new page will load which lists the changes that will be made if you confirm them. Check you are happy with the marks and then press Confirm. 
Another page will load that states the changes have now been made. Click the Continue button. 
You will then be taken to the student information table. In the Grades column you will now see the marks have been added to Moodle. 
It is possible that a student may submit late after you have done your marking. You can if you wish use the CSV file method. If this is the case then download the CSV file again and enter the mark for the student who has submitted. Save the CSV file and then upload it once and the mark should be populated. You can also update existing marks by following the same procedure. In practice, it is easier just to click in the text box beneath Grade and enter the mark there. 
Check the tick box beneath the Select column on the table. This should then check the boxes of all students.
A pop up box will appear asking Set marking workflow state for all selected submissions?, press OK.
You can also choose to Notify students in the drop-down menu below by selecting Yes. If you select Yes then the student will receive an email to say the mark has been released. If you would rather email them or post a message in the Announcements forum then leave this set to No. 
When you have selected Released and decided whether to notify the students press the Save changes button.
The page that contains all the submission information for students on the module will be loaded. In the Status column you should see that the status has now been changed to Released. This confirms that the marks have been released to the students. 
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