Project Properties Out of the Box "Settings" sub-page is not visible / listed under Project - Object - Views <Layout:Edit>
Administrator or users cannot delete Project Properties - Settings sub-page from PPM portal as it is an out of the box system sub-page.
You can run given database query to identify its existence at the database level and its current CAPTION <New Name>:
SELECT ID, CODE, VIEW_TYPE, PRINCIPAL_TYPE, VIEW_SUBTYPE, OBJECT_CODE, CAPTION, SEQUENCE, IS_SECURE, CREATED_DATE, CREATED_BY, LAST_UPDATED_DATE, LAST_UPDATED_BY FROM ODF_VIEWS WHERE VIEW_TYPE = 'property' AND OBJECT_CODE = 'project' AND CODE = 'finpropertiesUpdate.projectCreate'
Key is to identify CODE = 'finpropertiesUpdate.projectCreate' which is referencing to out of the box SETTINGS sub-page as shown in above screen shot.
If the CAPTION has a different value, then that's the new sub-page name which should be showing up under Project Properties - Object - Views. You can change it back to Settings or more suitable based on business requirement.
For On Demand client who doesn't have access to database can request CA Support to assist validate.