Hi there, I have actually tried that and it does not populates the list of available formats.If you run a “whatIs AEwhichCameraFilmback”, it leads to a procedure in an attribute editor template named AEwhichCameraFilmbackNew that’s found in the Maya installation files. Here you can see the proc that creates the contents of the drop down menu and the different procs called to update the UI. Most likely you can extend this or implement this in a custom window.