Only the Profile Manager(s) are able to edit the profile's LNAB.
Alexandria Eleanor is an orphaned profile. Just click on "[adopt this profile]" infront of "No Profile Manager" and you'll become the Profile Manager.
Add the source(s) you have. Then, on edit mode, click on "" infront of "Last Name at Birth", the "Fix the Last Name at Birth" screen will emerge. There you can change the LNAB based on the added source(s).