Edit is disabled and Delete option is missing Not able to edit or delete Global Navigation Items in Site navigation settings even though the user is a member of Site Owners Group. As in the below screenshot, the user is not getting delete button and edit button is disabled. Please suggest how to resolve it?
The behavior you are getting is because, the site is added in global navigation by SharePoint. If you scroll top in Navigation settings, you can see below settings done in it.
If you continue this settings, you will continue face this issue. To change the site title and URL you need to go to that site and change the settings there manually. Changes will be reflect to global navigation automatically.
The alternate solution for this is you deselect the "Show subsites" option and create your own heading for each site.