I have released a data field that let you switch off and on the rear light. I have tested on a TL 301 rear light but I have reports of users using it with the radar version, if you want to give it a try, it's here:
https://apps.garmin.com/it-IT/apps/b20762ef-7027-45d5-84fc-220777b7627f
It works only for devices with a touch screen, so 820 and 1000 series.
Short answer: No. The Wahoo units don't (yet) support ANT+ Light pairing, so when you switch the Radar to 'no light' mode with the button the Elemnt units see this as 'Radar Disconnected'. (Same happens with Edge units when it isn't also paired as an ANT+ Light).
This DataField & Widget can be configured to do what you are asking. I have it configured so it only flashes the light when it detects a vehicle though it is highly configurable via a companion web app
https://apps.garmin.com/en-US/apps/0d9fd828-c932-4470-9c37-fd2828881888
https://apps.garmin.com/en-US/apps/fa3c2332-76e3-4ba1-8528-32a0fd617ab1
Sorry, how is he supposed to install garmin CIQ apps on the wahoo device?:)
Apologies I misunderstood the OP. With this being a Garmin forum I'd automatically assumed you were also using a Garmin head unit without reading the full thread & forgetting that the Wahoo also supports the Varia. So it was just me being a pillock
Mine when I go to Light Mode -> Off, it's always off I can't adjust to other option like low. But I want the light off so I guess that's all done now.