1) Under Azure AD connect synchronization configuration export we list the Attribute which are excluded. This is a exclude only list and appears only when if you have used the wizard to select few attribute sync options.
You can check the view or export the current configuration and check for any attribute under excluded Attribute list :
Once exported, you can see the list of attributes which were excluded from sync. For eg in my lab scenario I excluded all these attribute from syncing :
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2) You can also go to the current configuration and Look for Azure AD attributes and select the view attributes option :
It will open a file which can show you which attribute are getting synced and are not removed :
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