Marking Single email Unread with chain of emails

This is what I did.

Select the email which you want to make as unread

Right swipe the email with 2 finger's. This will make all email's in that chain to be marked as unread

Now select another email from your inbox and go back to the email which you marked as unread.

Now Select the email which you marked as unread(Do not double click to open in a new window). This should give the email details on the right side and will go the original thread as this is the one which is unread.

Now scroll till the thread you want to see as READ

This should make only the email you want to see as unread