Which of the following can't you do in the custom metrics window?

The custom metrics window in Twitter Ads Manager is designed for customizing your reporting view, allowing you to tailor which data points you see and how they are arranged. You can easily change the column order to prioritize key metrics, and add or remove various metrics to focus on performance indicators relevant to your campaign goals. However, adding a new funding source is a financial and account management task, separate from report customization. Funding sources are managed in the account settings or billing section, not within the reporting interface.