Feedback Tools for Google Docs:
https://www.controlaltachieve.com/2016/09/docs-feedback-tools.html
Use the comment feature within G Suite products. When you select some text, an “add comment” button will appear to the right. Use this button to add feedback to students on specific sections
In Google Docs, there is also a Suggesting feature, where the edits you make appear as suggestions to students. They would then choose to accept the suggestion or ignore it.
Use Voice Notes instead of written comments. This allows students to listen to your feedback. This works similar to the text feedback option above. Select the text (or place your cursor on the spot) and click on the Voice Notes icon to record your feedback.
Source: https://docs.google.com/document/d/1spnvzfZIq5iYtld2IumzWzvLD7vFOlbHhylQ46LAbU0/edit#