...which was the wrong answer! I'm sorry, i made a big mistake! The only one of the both mentioned attributes which is not supported by the easyControl EC4P-xxx is 'PERSISTENT'. Thus, 'RETAIN' is supported (and works also well with e.g. occurring power failures). The only thing you've to bother is, that due to the lack of 'PERSISTANT' being supported, you will lose the saved NVRAM RETAIN data when you trigger a ‘complete’ download, instead of just using an online change. I'd like to apologize for any inconvenience resulted from my mistake!