I'am searching for a list of API's to manage application and packages via powershell.
With AV2.x we used a script for automating appvolumes what we want to use with 4.x too.
There is no public App Volumes 4.x API yet. You could use developer tools in the browser to discover the API endpoints in 4.x - that is what I did to develop some Flings. Just note that the API endpoints may change and there is no support for this API.