Since a dynamic folders do not have the ability to set RDS gateway settings, the "RDSGatewayFromParent" property shouldn't be considered a valid option for objects created by a dynamic folder script.
Please allow an option to set the parent folder of a dynamic folder be the referenced object for this property, or add the RDS Gateway properties to dynamic folders.
it's true that Dynamic Folder objects currently don't have the ability to configure a Remote Desktop Gateway. This is definitely something we could add in a future update.
However, the RemoteDesktopGatewayFromParent rJSON property does still make sense. That's because within your rJSON, you can create subfolders which can have RDS gateways configured. You can then set "RemoteDesktopGatewayFromParent" to true on dynamically created connections to inherit the RDS gateway settings from their parent folder.
You can read more about creating folder hierarchies in rJSON here: https://docs.royalapps.com/r2023/scripting/rjson/building-folder-hierachies.html
Hope that helps!