First of all, HiBy has moved to a new generation of application core engine. N5ii and N5iiS is using HiBy 2.0 core, and the current HiByLink through WiFI is implemented under HiBy.3.0 Core. To the best of my knowledge, HiBy R6 is the first DAP developed under HiBy3.0 core. In other word, the current WiFi HiBy will not be directly applicable to N5ii or N5iiS unless HiBy will transfer their latest WiFi HiByLink feature from HiBy3.0 to HiBy2.0. I have no idea whether this is technically feasible and Cayin cannot commit anything on behalf of HiBy along this line. If you treat My Favorite as a playlist, then you can add song to this playlist conveniently. If you want to this function to extend to any playlist at anytime of playing, I think you are referring to Dynamic playlist, this is certainly not a commonly available feature among DAP and is fairly complicated to implement. I have seen Rockbox doing similar things but we can't replicate that in Cayin's system easily.