If you get a 504 when deploying from Web IDE Full-Stack set the additional property HTML5.SocketReadTimeoutInSeconds to 300 on your SAP Cloud Platform destination (Cockpit>Connectivity>Destinations).
In my case I was deploying to a Netweaver Gateway system and it kept getting stuck on one file before throwing a 504 error. Setting the property resolved the issue. It is listed in the Web IDE documentation, but the path to the answer is rather convoluted, so I thought I would share it here.
Note that the property name won’t appear in the dropdown list, but that doesn’t matter.