Googling suggests that I highlight the name with my mouse and hit delete - this doesn't work (the name stays in the dropdown list, I instead end up deleting a letter from the name textfield)
A Mac specific suggestion is to hold down the "fn" button when I click delete. Trying that seems to have no effect - nothing changes, that I can see.
How do I remove a specific username from the username drop down on Google Chrome on Mac?
To all the answers suggesting Control ⌃+Shift ⇧+Delete ⌫ It is an editor shortcut for "quick delete entire line". So it only looks like it works.
It does not add/modify/delete names from the list of login names that are suggested for autofill.
Please test your answer before posting - make sure that the auto-fill list is actually different after you've deleted a name.