On the page:
You can set the visibility of the fields in most of the analytics events types with the exception of custom events. Hiding fields in custom events is not supported.
The Manage Fields permission is required to manage field visibility. If a role has the Manage Fields permission, it means all the users with that role can manage all the fields they have access to. They can unhide the fields or see which fields have been hidden. For instance, if you have "Manage Fields" permission and "Transaction" permission" for the application "Ecommerce App" then you can only see and manage fields for that application.
In 4.3, you may have two types of extracted fields, fields created in 4.2 where the controller version has been upgraded to 4.3 and fields extracted from logs with log source rules.
For fields created in 4.2, you can delete the fields using these steps:
For fields being extracted from logs using log source rules, you can delete the fields by editing the source rules. See Field Extraction for Source Rules.