Is there a way to, and if not, I would like to make a feature request to have an easy way to disable internet traffic on the router both for all devices and for specific individual devices 

I used to run Asus routers and in their firmwares they had a feature where you could disable internet access on all devices connected to the router and/or individual devices while maintaining local network connections between all those connected devices  The only way I can see disconnecting internet on the C5400X is by disconnecting the actual ethernet cord between router and cable modem, and this affects all devices.

Also, when trying to use the Whitelist feature on the router under Access Control, the router will hang (or maybe its the firmware user interface portal on the web browser locking up) if you use the toggle all checkbox and then click Delete .  I have about 36 connected devices (switches, NAS, smart switches, speakers, etc) and adding/removing each one can be tedious.