There is no dedicated parameter to add a header in oData v2 connector calls. However, if you are using a token for authentication, you can set it in the login method of the connector.
Login methods are credentials that will be used by the connector for authentication: https://community.simplifier.io/doc/current-release/integrate/connectors/login-methods/
Create a new login method, set the type to ‘token’ and activate the advanced view. For a static token, set the source to ‘provided source’. Set the target to ‘header parameter’.
Then, enter the static token. Set the header name according to your API, e.g., ‘Authentication’. Now, the token will be added as header parameter in each connector call.
Read more about the login method ‘token’ in the documentation: https://community.simplifier.io/doc/current-release/integrate/connectors/login-methods/token/