On the Ringcentral Phone desktop app you can very easily add a custom fax page. However that option is not available on the new Ringcentral (Glip) desk top app. Please bring it back! It was so easy and a great thing for many companies!
We would also love to see this feature be implemented in the Glip app, especially now that support for the RingCentral Phone app is ending in July. My company uses the Glip Web App, and faxing with our own cover sheets attachment, is slow and inefficient.