Above should be applicable to the SPIP335 as I am not aware of this phone having a dedicated Softkey for DND.
For the new VVX500/600/300/400 series this is at present not applicable and requires a Feature request via your Polycom reseller in conjunction with a Polycom sales engineer.
Please ensure to provide some feedback if this reply has helped you so other users can profit from your experience.
Polycom Global Services
---------------- The title Polycom Employee & Community Manager is a community setting and does not reflect my role. I am just a simple volunteer in the community like everybody else. My official "day" Job is 3rd Level support at Poly but I am unable to provide official support via the community.
Notice: This community forum is not an official Poly support resource, thus responses from Poly employees, partners, and customers alike are best-effort in attempts to share learned knowledge. If you need immediate and/or official assistance please open a service ticket through your proper support channels. Please also ensure you always check the VoIP , Video Endpoint , Skype for Business , PSTN or RPM FAQ's