Here you can add, edit, or remove Preserved Request Header settings for the identified API Definitions.
By Selecting "Synchronize Edits", any changes you make will be reflected, if possible, among all Preserved Request Header settings for API Definitions having the same name within the same domain, unless the changes are being made to newly added rows.
New rows are treated as their own group. This is to protect existing values from being arbitrarily changed to blank values found within new rows.