Log in as a regular user
Create a single-chapter draft work and make note of its URL
Post > New Work
Fill in required information
Press "Preview"
Press "Save Without Posting"
Make a note of the URL of the draft work
Create a multi-chapter draft work and make note of its URL
Repeat the first 3 steps for creating a single-chapter draft work
Follow "Add Chapter"
Fill in required information
Press "Preview"
Press "Save Without Posting"
Make a note of the URL of the draft work
Create a posted work with a draft chapter and note the URL
Post > New Work
Fill in required information
Press "Post Without Preview"
Follow "Add Chapter"
Fill in required information
Press "Preview"
Press "Save Without Posting"
Make note of the URL (ideally for the draft chapter itself, e.g. https://test.archiveofourown.org/works/1070223/chapters/2139585 )
Log in as admin
Attempt to go to each of the URLs you noted
What happens
You can access the single chapter draft.
The multi-chapter draft redirects you to the homepage with a blue flash error that says, "Please log out of your admin account first!"
The URL for the draft chapter does the same redirect with flash error.
If you edit that URL down to just its work bit ( https://test.archiveofourown.org/works/1070223), it only shows the posted chapter.
What should happen
You should be able to see the multi-chapter draft and the draft chapter.
If you go to the dashboard for the draft's creator, you should also be able to see and access their Drafts page from the sidebar.